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Forum Categories => Tractors => Topic started by: cobbadog on 19 October, 2019, 10:58:23 am

Title: Carby ??
Post by: cobbadog on 19 October, 2019, 10:58:23 am
As you may know I've been having issues with getting the David Brown Cropmaster running properly. It would appear that the silly little spring on the needle and seat has been a fair amount of the problem and with this removed it no longer starves for fuel, yippee!
Next problem is air mixture. The engine runs rich and at idle sends up black smoke from the chimney. No matter where the air mixture screw is, all the way in or almost out of the carby it makes no difference to the way it runs. On full revs it runs ok but has flat spots when it revs up from idle. Not coughing just hesitating a few times then it revs fine.
I have had the carby totally apart, made new seals for the throttle shaft but the old ones I fitted a while back, "O" rings were in perfect shape but the latest thing they suggest to fit is nylon washers so I did that as well to get the best seal possible. All galleries are perfectly clear as you can clearly see through them all. Main jet tube and jet are clean as and so is the bowl.

Any clues to solving this problem please?
Title: Re: Carby ??
Post by: asw120 on 19 October, 2019, 08:33:07 pm
Not much comes to mind, but....
Blocked breather hole,
High fuel level.
Have you tried to see if the idle comes good after turning the fuel off and letting it run out of fuel?
If it cleans up and revs like a Victa when the fuel is turned off, I would think fuel level.
I wonder if there is a drain you could put a drilled out screw in with some clear nylon hose on it to see the fuel level when running?
Mt Inter was doing this a while back. Was a tiny piece of crap in the needle and seat.
I'd live to know what you find in the end.

Title: Re: Carby ??
Post by: cobbadog on 19 October, 2019, 09:45:38 pm
Cheers mate.
I always shut the fuel off when shutting it down as I dont like leaving fuel in the bowl. By doing this it made no difference to the way it runs.
With the fuel level I also thought of this so I installed another washer under the needle and seat to lower the seat down which in turn lowers the fuel level. On this carby the needle and seat fit into the top of the carby body and the only way to adjust fuel level is to add or remove washers. Fortunately there is a drain tap on the bottom of the bowl as this is a TVO engine (petrol/kero) so I can fit a clear tube onto that and face it upwards to see the level but since adding the extra washer the carby has stopped flooding but your idea is a good one and needs to be checked.
The needle n seat are crystal clear and no crap inside anywhere in the carby. Both jets and the jet tube are seating properly and are clear.
What I have found that has been contributing is a coil lead that is not quite up to scratch on the multimeter and one HT lead was not right and giving a bad reading. So I will get some new leads on Monday along with new fittings.
Next out came the plugs. Black as charcoal. Cleaned them up on the wire wheel and pushed a brush up inside the recess of the plug and tapped it on the bench and a heap dropped out. Kept doing this until all was clear. Ran the multimeter over these as well and still found one was not right so a new set of plugs on Monday if they have stock.
Last was the points. Looking at them they were in good condition with no pitting at all. I still gave them a rub with the points file and then checked the gap.
So I put the plugs in and did a start up and it sounded alright so I took it for a run down the street. Got going and wasn't too bad but a couple of minutes later it played up so chucked a u-turn and parked him up until I get the leads and plugs.
The story continues soon.
Title: Re: Carby ??
Post by: cobbadog on 21 October, 2019, 02:38:21 pm
Still playing with this and thought of a few things last night after receiving a link to Solex Carbies cleaning and tuning them.
First thought was, is the blanking plug opposite the bleed screw (air mixture screw) suppose to be open to allow air in. NO. It is a blanking plug and although it looks like a jet from the outside it is definitely a blanking plug.
Then were all the jets the correct size. YES.
Again are the galleries clear from blockages. YES.
Title: Re: Carby ??
Post by: cobbadog on 21 October, 2019, 02:47:49 pm
Next was again making sure everything else was where it was suppose to be and work out where does the air come from and go to. SO I have put up pics of the top and bottom side by side and then marked with an arrow where the air comes from and goes to. Although it is tricky to see, you should try taking a pic of it, there are no blockages but at least I now know roughly where the air bleed screw should be to start metering the air flow. The link posted has been a great help and I have confirmed the jet sizes with the chart and only the main jet is slightly different being a little bit larger than middle of the road on the charts. But this should not effect the running rich at idle and the idle jet (g) on the chart I think is the right size as I cannot read it properly.
Title: Re: Carby ??
Post by: cobbadog on 21 October, 2019, 04:49:12 pm
Something I have just now noticed is what I thought was the blanking plug marked as "W" is not and it is the screw to hold the choke tube in place. In the picture of the Solex FV carby there is no sign of the air bleed screw or the plug, yet it is there on the carby and is mentioned in the section on 'slow running pages 14 -16 on how to adjust it.
Title: Re: Carby ??
Post by: cobbadog on 22 October, 2019, 09:04:35 pm
Picked up some new plugs today while in town and called into Rustic Spares for the new plug leads to make up myself along with all the new connections. Then John suggested a new needle and seat and so I took a couple home to try. Had every intention to fit the needle n seat, make the new plug leads and fit the new plugs and then the phone rang with work so all this has to wait until tomorrow afternoon.
Title: Re: Carby ??
Post by: asw120 on 22 October, 2019, 10:34:21 pm
As you say it runs just the same until it stops after you turn the fuel off, I am thinking a high fuel level is not the problem.

I am wondering now, how did it run before the rebuild? I missed that bit.

For the record; I have had oversized mains affect the idle adjustment on a car, twice now - both times with aftermarket Holleys (a 350 - two barrel and a 600 - four barrel) They would idle with the screws bedded until I put smaller mains in. Having said that, they are very different to what you are working on.
I have also had a perforated power valve give a very rich idle, but I highly doubt you have one of those.

Wisely, you are not neglecting the electrics. Be interesting if something there fixes it.

Finally, I forget now, do you have even compression? (no leaky intake valves blowing back through the carby and picking up fuel twice for that cylinder)

Your updates are much appreciated; we have all had these sort of troubles and I usually learn something from threads like this one.

Don't despair - you will get it!

Title: Re: Carby ??
Post by: cobbadog on 23 October, 2019, 07:49:37 am
G'day Jarrod,
Yeah before the paint work and being off the road for about 12 months as I did brakes and oil seals inthe back end, changed the front axle over from another tractor but the engine was done a few years back and used to run fairly well and nothing like this mess. No compression tester to do that but that is another option to look at if the electrics dont help resolve the issue.
Not pissed off about the troubles just annoyed.
Title: Re: Carby ??
Post by: cobbadog on 23 October, 2019, 03:53:16 pm
Latest update !
Well I made all new HT leads and one for the coil. All tested perfect once made then again fitted into the cap. All new plugs fitted and the needle and seats that I bought home do not fit so they can be returned to John, thanks John for the loan.

So now I know exactly what it is NOT. Non of the above or I am confident it's not the carby.

From start up today I got a whole new set of issues and the main one is backfiring. So next attempt is to check the timing and fix that if required, then try a new coil and see where that takes me.

Title: Re: Carby ??
Post by: cobbadog on 24 October, 2019, 02:46:05 pm
Well guess who swapped #1 n #2 plugs leads over causing the back firing?   ME  !!!!!!
That sorted that issue and then I did the start up and it jumped straight to life but still running rich. So back to the bleed screw (air mixture screw for us Aussies). I slowly a bit at a time wound it out a 1/4 of a turn at a time and not making any difference until I actually pulled the screw all the way out. The immediate result was the engine sounded smoother like it use to sound, so this points me back to the carby yet again.
Ever feel like you are going around in circles?
Anyway, in the pic below that I posted before it shows you both top and bottom of the carby and where the screw goes through. So the screw makes no difference until it is removed in total so that points me to the last of the 3 openings, the one closest to the head of the screw is somehow different to the one on the opposite side but they look identical when you poke around in there and shine a torch. It actually waits until the screw is all the way out, not just at the point where the taper would be above the 3 hole.

Any clues please?
Title: Re: Carby ??
Post by: cobbadog on 26 October, 2019, 02:50:31 pm
Episode 1,234, way too many.
Once again a night of ideas on what to do to resolve this mess. Fuel level in the bowl was measured by connecting a clear plastic tube to the drain cock on the bowl and holding the tube agaist the bowl. Level was about 3/4 full. I have an aluminium washer under the needle n seat and this raises the level too high, to the top of the bowl and floods so went back to having a fibre washer with the aluminium one and back to being 3/4 full. At the moment it does not starve on full throttle standing still but might when on the road, will find this out tomorrow on a quick run up to the forrest and back.
Next was to once again strip the czrby down to being completely apart and double checking cleanliness and re-assembly ensuring that the 3 parts of the main jet are assembled correctly and fitted firmly in place.
Then with yet another read of the Solex carby link something hit me hard in the face, bloody air cleaner. This runs an oil bath cleaner and when I dropped the bowl it was not only over full but the centre ring where the air breaths in was also full of oil. So I lowered the oil level and removed the oil from the middle. Hopefully this was the right thing to do.
Still with the oil bowl off I started the tractor and ran it for a while so it was warm. Then I dropped the idle screw right back so it was not touching the stop and all the time changing the mixture although it did not seem to do much. So I kept winding the mixture screw out until it was in my hand. You can hear the air rushing in through the hole and when you put your finger over the hole the engine revs drop and runs a bit rough. Threw the oil bowl back on and nothing changed there so that is done. There is a remote chance that there is still oil inside the air cleaner where the steel wool looking stuf is and may still be choking the engine. Maybe after the run tomorrow this too will improve.
With a couple of runs up and down the back driveway it certainly pulls well with no hesitation at all where in the past it did. SO if nothing else this has improved.
All I can do now is take it for a run up hill and down dale and along the road and give it a good gallop and re access it from there.
Title: Re: Carby ??
Post by: cobbadog on 27 October, 2019, 04:48:13 pm
Thought I may have had this beat but no unfortunately. The further we drove the worse it got but at least we got there and back for a picture shoot so here are a couple of him in the local State Forrest just a few kilometers from home.
Since getting home I have removed the plugs and cleaned them again as they are black as can be, checked the HT leads with the multimeter, removed the coil and condensor and hooked them up to my testing machine which rates the condensor, checks it for leakage and then tests it. The coil then is connected and a voltage is sent through it and you adjust the gap in the round window to produce a good constant spark over the widest gap on the lowest voltage. Once this is set you then select 'heat' and this heats the coil as if it is on the engine and running at temp. After minutes of heating then switch to test again. I got the same result after the heating which shows it is in good working order. I then removed the points and dressed them up and also found there was a small amount of oil on the base plate so I cleaned this all up with carby cleaner and a soft rag. Put it all back together and still the same. Back on the other side the oil bath bowl is off again to check that oil has not got back into the centre section again but it is clear now.
Title: Re: Carby ??
Post by: cobbadog on 29 October, 2019, 04:26:54 pm
While waiting for the new needle and seat to arrive I bought a compression tester today and tried it out. I did the test on a cold engine, not sure if that is the right thing to do and got the following readings;
1 - 75 psi
2 - 75 psi
3 - 72 psi
4 - 75 psi
Each held the pressure for a short time before I released the pressure.

So the question now is, what should the pressure be and should I have done it hot? I looked in my workshop manual and it gives you all the specs like bore diameter x stroke, cu in, bhp and a compression ration of 4.7:1 but no numbers on what compression it should have.
Title: Re: Carby ??
Post by: asw120 on 29 October, 2019, 04:59:44 pm
Sounds like good numbers to me. I figure you would hear if it was blowing out the intake.

Title: Re: Carby ??
Post by: cobbadog on 29 October, 2019, 09:20:32 pm
It does seem to hold pressure for the short time, 30 seconds before I release it with the button so I think that the valves and rings seem to be ok.
As for any leaks caccuum or exhaust I cannot hear any and a spray of start ya bastard does not alter the revs so its not sucking in air anywhere along the manifold or the flange gasket to carby.
So it can now sit around untl the new needle n seat arrive and start again.
Title: Re: Carby ??
Post by: asw120 on 30 October, 2019, 07:54:21 am
If it's like most compression testers, that valve is to hold the pressure in the gauge so you get time to read it.
I don't think even good cylinders hold pressure very long.

Title: Re: Carby ??
Post by: cobbadog on 30 October, 2019, 04:24:22 pm
Apparently these are good numbers. Formula offered up to me was air pressure x 4.7 which is the compression ration.
14.7 x 4.7 = 69.09 psi and I have a good average above that at 74.25 psi. This may now be considered to be a high performance engine with a ratio like that!
New needle and seat arrived today from Classic Carbs on the Gold Coast. It is a genuine Zenith part which fits the Solex perfectly. It also came with a choice of 2 thicknesses of fibre gasket to adjust the fuel level. Tomorrow hopefully I will put it back together and see what happens.
Title: Re: Carby ??
Post by: cobbadog on 30 October, 2019, 09:19:26 pm
Scotty also offered up the idea of checking valve clearance especially on #3 as the problem got worse as time went on, heating up more.
Time will tell I guess.
Title: Re: Carby ??
Post by: cobbadog on 31 October, 2019, 04:57:09 pm
I have been using that "doing word" an awful lot but then I always do anyway, so nothing has changed.
So, just for everyone's amusement I got to have a short play with it today.
Fitted the new needle and seat using the thin washer. Then as described in the manual remove the main jet and with the top half of the carby bolted to the manifold and connected to the fuel supply and throttle linkage you can then swing the bowl out towards you and then turn on the fuel and watch where the fuel level comes up to. Right on spec, it stopped about 2-3mm from the top of the jet holder. Beauty one mate, I'm winning and all that stuff. Screwed the bowl back on and turn the fuel on and I waited and all seemed good, no fuel dripping out. Tried a start up and no go. then while switching off the ignition fuel starts dripping out. "LOTS OF DOING WORDS RIGHT AT THIS MOMENT"
Removed the bowl and fitted the thicker washer but still dripped. Then I noticed the float has a small dent in the top and I am now thinking that this might be the cause of it not shutting off properly all the time.
So I am chasing a new float for the Solex 30-FV if anyone has one, it should have 26 gm (26 grams) stamped on top. You can just see the small dent on the top and I dont want to be the one to try and take the top off the float, knock the dent out and try and put it back together. I just know what will happen.
Title: Re: Carby ??
Post by: cobbadog on 02 November, 2019, 03:45:36 pm
In today's episode, we explore the internals of the engine. I pulled the rocker cover off and checked the clearances of the valves. A couple were slightly tight but still had plenty of clearance when running warm. So I went through all of them and checked the gaps and made them as specified. Typical Pommies don't give you a COLD setting only HOT so at the moment they are set cold to the gaps suggested. I lost spark at one stage and went hunting and in the end I looked closely at were the power enters the dizzy. The bolt ran close to ground so I put a short piece of insulation under it and that appears to have solved that problem. I did have a go at the float. I opened the hole at the bottom of the float and used a piece of fencing wire, (the most handiest tool on a farm) to push up the small dent at the top. I did have to bump it a little with a hammer but got it up fairly close. So with the rocker cover off I did a start up and took this video. It still does not run smooth and with out touching anything it occasionally picks up the revs slightly and goes back to running rough again. If I pick the revs up a little the engine still runs rough but not as bad but then spreads the love of oil to everyone nearby.
Title: Re: Carby ??
Post by: cobbadog on 03 November, 2019, 02:19:54 pm
All sorts of things have been going on and each time directing you to the opposite side of the engine. Today after re-doing the valve clearances to Exhaust 0.022" and Inlet 0.015" I did find 2 that were tight but not that tight I could not get the feeler gauges in so I backed them off ever so slightly. While running the engine with the cover off you can see in the video a large amount of oil running out of the rocker shaft at the mid point. This is where the front and rear shafts meet and then there is a small lock screw to hold it into the post. On top of the post there is a hole with no thread and you can see to the bottom of the shaft when the engine is off and the oil drained out. I thought this was a waste of good oil pressure because if I put my finger over this hole more oil went to the rockers were I feel it is suppose to go to. So I made a modification by dropping a small bolt down the hole but not fr enough to block the hollow in the shaft and then wired it in place. Now more oil goes to where it is supposed to go to and the rockers will be happier.
I did borrow a carby today off a mates known to be good tractor and bolted it to mine. It pretty much started up just as normal, easily, but went straight to this uneven running as if spark was the issue. So I went and started pulling the HT leads off one at a time and pushing them back on. # of the 4 virtually made very little difference as to how it was running. When I went to push the lead back on a huge spark jumps across to the plug and for a moment that plug would fire then stop again. So I replaced the 3 plugs with some of the old ones I took out and this improved matters a lot but then I was back over to the carby as the engine was hunting a little bit. At this stage no black smoke at or near idle or at revs so that is good. So I started adjusting the spring tension on the throttle linkage between the governor to the throttle main shaft and I have managed to settle that down to running constant. Back to the air mixture to try and get rid of a flat spot and so far no joy but it is very small and although I have not driven it as yet the flat spot is the least of the issue.
Title: Re: Carby ??
Post by: cobbadog on 04 November, 2019, 04:22:42 pm
The engine is now running far better with room for improvement. I fitted up the borrowed carby and started the engine. It was missing on a number of cylinders but had a huge spark at each plug and only 1 1/2 cylinders appeared to be firing. Swapped over the ones not firing well with 3 old plugs and it this improved things but still not happy. dug out the timing light and removed the cover on the bell housing and turned the engine over to approaching TDC and the marks were coming up. The manual says to put the letter "M" in the centre of the hole, I have no pointer on mine, and at this point the points should be just breaking but mine were opened more than 'just'. So using a test lamp I loosened the distributor bracket and rotated the it back so that the light was on and slowly rotated the distributor until the light just went out. At this stage this is where the manual tells you to set it to and should be 7' BTDC. It started up ok but was occasionally back firing through the exhaust so I moved it a little bit and until the engine sounded as smooth as it could be at this stage. I lock it up at this point and went back around to the carby where on full throttle the engine was not too bad but at idle it was not quite so good and I moved the mixture and got it as good as it could be. Came back after lunch and swapped the carby over to using mine. Started ok, idled sort of, very little black smoke but on full throttle the revs were up and down so I adjusted the spring tension on the throttle linkage and this settled down nicely to a constant running engine at full throttle. Back it off to idle and got a back fire through the exhaust but at least it was now idling with almost no smoke but when I pulled the throttle on full and fast there is a hesitation. This to me is a mixture problem but no matter where I adjust the mixture screw it made little difference but I have found a spot where it is at the least amount. I drove the tractor up and down the drive way but this is not good enough to test it so will do a road run tomorrow and see where I am at.

I did end up with my timing light connected and managed to get the light around the engine to the inspection hole on the opposite side and reading from #1 HT lead I do not see any marks on my flywheel. The same goes on the other 3 leads, any clues on this one?
Title: Re: Carby ??
Post by: franco on 05 November, 2019, 10:28:13 am
QUOTE: I did end up with my timing light connected and managed to get the light around the engine to the inspection hole on the opposite side and reading from #1 HT lead I do not see any marks on my flywheel. The same goes on the other 3 leads, any clues on this one?

Flywheel not correctly aligned with crankshaft? I have struck this several times on old vehicles where the flywheel had been removed at some stage and replaced incorrectly,  i.e. not aligned with the correct holes on the crankshaft flange. I suspect this might have been done deliberately sometimes on 4 cylinder engines with 6 crankshaft flange bolt holes to make use of an unworn section of the starter ring gear where the starter normally engages it.

Title: Re: Carby ??
Post by: cobbadog on 05 November, 2019, 09:55:31 pm
Hi Franco,
This one can only go on one way, it's not an option to re-position it. But a similar problem happened up the front end. Atone stage a bolt inside the timing cover came out and went through the timing gears. It damaged a couple ot teeth on the governor gear and must have destroyed the cam gear as the original timing mark on the cam gear is way out. I noticed this when I was tripping the engine down and fortunately I marked it correctly. I since found that this gear belongs on a diesel model not TVO. But that worked well when it went back together all that time ago.
The dizzy on this is not unlike an early Ferd, it can only go in one way but you must align the drive lug with the oil pump. So at worse it can only be a few degrees out but has a huge adjustment by undoing the clamp on its base. So the next step is to lift the rocker cover again and makes sure it is on compression, get the letter "M" in the middle of the hole at the flywheel and ensure that the rotor is facing #1 position on the cap with the points just breaking.
Title: Re: Carby ??
Post by: cobbadog on 07 November, 2019, 04:29:25 pm
Well I went way back to the beginning of the basics even looking under the base plate of the dizzy and found the bob weights were free and in working condition so this was sorted. Re-assembled the dizzy and checked that I was at the "M" mark on the flywheel which gives me 7' BTDC and on compression stroke with both valves fully closed. Gaped the points to 0.012" and connected the test lamp to find where the points were just breaking and the light goes out, locked in place. Again cleaned the plugs check the gap at 0.022" and replaced them along with the HT leads. Went around and switched the fuel on waited a bit to see if any leaks came along then started the engine, broom broom. Let it run for a while and connected the air cleaner back up and a slight tweak with the mixture screw and ran it at various revs. Still a tiny bit rich at idle but after all this crap I am happy with that. Took it out for a road test and it went well. About a 15 minute run was enough to say that it is running and almost better than before the paint job. The governor seems a bit slow in opening and I am not sure if this is an adjustment or a throttle linkage issue but it still went well pulling away easily up a steep hill at very low revs in H 3rd so this is a good thing. I finally found the markings for this dizzy, it is a CA10 model made in 11/53. Will do a bigger road run when we get back from a short break but it should be all good.
Thanks to all replies and ideas in helping to solve this issue.
Title: Re: Carby ??
Post by: wee-allis on 16 December, 2019, 08:58:08 pm

John, not related to this or any post, but I've sent you a PM.
Title: Re: Carby ??
Post by: cobbadog on 16 December, 2019, 09:36:21 pm
Thank you Steve. Message received and understood plus replied to in a positive way. Thank you once again.
Title: Re: Carby ??
Post by: shubys tractor farm on 06 January, 2020, 05:53:56 pm
I have over 30 DB's - almost all models up to the white units. First thing I would check is the fuel tank. Most times -  they are full of sediment and that blocks a vertical sieve on the outlet inside the tank.  IT IS THE FIRST THING I DO WITH THESE TRACTORS----TAKE OFF THE FUEL TANK AND CLEAN IT OUT COMPLETELY.  Perhaps try that (If not done all ready. Happy new year to all ---------------
Title: Re: Carby ??
Post by: cobbadog on 06 January, 2020, 09:34:12 pm
Thanks shuby but further back in the thread the tank was removed and fully treated with the KBS fuel tank cleaning and sealing kit so is spotlessly clean inside, probably better than new.
What ever was pissing it off seems to have almost gone away now. Still need time to go out on another run to see what happens but lately it is getting way too hot and all too soon weather wise plus even though I could do a road run I dont want to start any more fires around here.
Thanks for the input though.
Title: Re: Carby ??
Post by: shubys tractor farm on 13 January, 2020, 08:31:47 pm
Sorry --  I DIDN.T READ ALL THE PREVIOUS HISTORY - Seems like a book is coming out of this saga.   Hey - just a silly comment to something  I DID read in earlier posts.  My dad used to cross over no 2 and no3 spark plug leads deliberately - on a 4 cyl motor = when the motor was running "SOUR" and this would cause a backfire through the carby----and guess what - the motor ran smooth thereafter.  I would not recommend this treatment to be used - just a comment.  I admire your persistence. Shubys tractor farm.
Title: Re: Carby ??
Post by: cobbadog on 13 January, 2020, 10:00:32 pm
We used to go to auctions to buy paddock bashers and do the same thing, swap a couple of leads over, buy it real cheap with a few days rego on it, put the leads abck in place and go for it.
If this saga was to be put on paper the bloody greenies would kill me for knocking down a forrest. When the tractor was stripped to do the last bits and pieces then start on the tinware, it ran like a clock. For one reason or another that was 12 months before I got it painted and back together and after so many things being checked, replaced even borrowing a carby twice off a mate to see where the problem was took all of my patience and the neighbours learnt some new words in me doing so. I still appologise to them each time I see them.
In the end, it was not just one thing but a combination of nearly everything. I think I still hold the record for dropping the carby off, stripping it, inspecting it and fitting it back on a Cropmaster, I still have nightmares over the carby, better have another Panadol.