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Post by zambia on May 14, 2022 21:20:54 GMT -5
Guys..I need some help!!
I'm having trouble with my H2 since a top end rebuild. I've tried 100 things and have also been driving Johnny O and Ned crazy.
Bike was bored to 72mm this winter and new pistons installed .. was running fine last year but quite a bit of piston slap, hence the rebuild. It went together fine and started quite easily..then the trouble began.
At first I could not get it to idle under 3k .. there were no air leaks but definitely seemed like a carb problem. I won't bore you with the details .. eventually I took my time and properly cleaned, sync'd, set floats and fuel heights..blah blah. But the centre cylinder was drowning and backfiring like a world champion at a chili eating contest.
I've swapped carbs and the problem remains with the centre. So far I have done the following:
- reset timing to perfection
- new plugs
- checked all stator pickup coils for resistance
- checked and swapped in a spare ignition coil
- changed plug wire
- swapped in spare CDI box
- spark looks decent - similar to left and right
- compression 140+ on all cylinders
Today after lowering the fuel level on all 3 carbs, I got a good idle and "normal" throttle response. There was an odd backfire, but not much. Suited up and went for a ride. The bike ran well .. not 100%, not perfectly crisp and an occasional misfire., but pretty well. I turned down my favourite country road (slopes slightly down hill) rolled on the throttle in second gear and the lofted the wheel for a good 100 yards - then the centre cylinder dropped. Fouled plug. I'm almost at the end of my rope!
Thanks in advance!
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Post by H2 Dude on May 14, 2022 22:55:56 GMT -5
I have no idea Ian other than maybe stuck check valve allowing too much oil.I did have this happen on my old 74 GT 750.
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Post by lc on May 15, 2022 17:09:00 GMT -5
I have no idea Ian other than maybe stuck check valve allowing too much oil.I did have this happen on my old 74 GT 750. +1. Who does your cylinder boring Zed? J |
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Post by zambia on May 15, 2022 20:32:35 GMT -5
I have no idea Ian other than maybe stuck check valve allowing too much oil.I did have this happen on my old 74 GT 750. +1. Who does your cylinder boring Zed? J I had it done by Twin Seasons in Georgetown - great guy, does nice work! He did my TZR 250 as well. I think I've got this down to an electrical misfire - ruled out CDI (unless all 3 spare units I have are bad).. so I might have to swap the stator. |
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Post by autofobe on May 16, 2022 12:04:23 GMT -5
Maybe your centre coil is breaking down and loading plug. I never trusted the NGK plugs,always use champion.To many NGK knock off’s out there.
You might want to go to a little cooler plug.
Brad
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Post by Walms on May 16, 2022 14:13:39 GMT -5
You may remember my bad solder joint on my stator that had me doing electrical checks forever... I never had anything resembling a backfire though, could it mean a timing issue?
Have you checked the primary and secondary coils yet? Also, maybe a timing light to confirm all 3 cylinders timing.
Maybe try swapping carbs to see if problem follows.
You mention that you checked for air leaks...
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Post by pipe welder on May 17, 2022 7:33:49 GMT -5
You mentioned that the center cylinder was flooding then you said “the centre cylinder was drowning and backfiring like a world champion at a chili eating contest. I've swapped carbs and the problem remains with the centre.” Is it possible that you are getting some contamination in the fuel or bad gas. Hard to explain why the flooding issue remained after swapping the carb out. Obviously fuel problems should affect all the carbs but swapping out that carb should have stopped the flooding.
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Post by Walms on May 17, 2022 8:24:25 GMT -5
I've never had a backfire from too much gas.
It might be a good idea to triple check wiring, coils and swap out stator.
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Post by kawonda750 on May 17, 2022 8:27:42 GMT -5
I would look at the coil and centre cylinder timing. I have some coils here if you need one. Of course, asking you about parts is like bringing sand to the beach....
I do like the world champ/ chili eating contest though...
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Post by zambia on May 17, 2022 14:23:46 GMT -5
You mentioned that the center cylinder was flooding then you said “the centre cylinder was drowning and backfiring like a world champion at a chili eating contest. I've swapped carbs and the problem remains with the centre.” Is it possible that you are getting some contamination in the fuel or bad gas. Hard to explain why the flooding issue remained after swapping the carb out. Obviously fuel problems should affect all the carbs but swapping out that carb should have stopped the flooding. Hey Jim - I guess my report is misleading.. I did swap the carbs and since the centre seems to fire intermittently it floods ..but I believe it floods because of the misfire - not the reverse (misfires because of a flood) |
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Post by zambia on May 17, 2022 14:29:15 GMT -5
You may remember my bad solder joint on my stator that had me doing electrical checks forever... I never had anything resembling a backfire though, could it mean a timing issue? Have you checked the primary and secondary coils yet? Also, maybe a timing light to confirm all 3 cylinders timing. Maybe try swapping carbs to see if problem follows. You mention that you checked for air leaks... The offending pickup wire has been soldered on my stator - I did it once (poorly) and Soup did it a year after that. I re-soldered on Sunday and that made things worse! So I need to rethink my plumbing solder fix. MRAXL (Dale) suggests I undo the plumbing fix (it's a serious, solid join but maybe not as conductive as it should be). |
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Post by Curtis on May 18, 2022 4:35:26 GMT -5
You should be able to check on each side of the solder joint with a multimeter OHMs - a large solder joint doesn’t mean squat if it has high resistance.
Check that before disabling the unit and chasing your tail. If it Ohms out OK I would then do a peak output test on each stator pickup coil and compare to the other cylinders before condemning the stator. If you do not have a peak voltage adapter for your meter you can do a resistance test between each pickup coil and compare the values (they should all be the same or extremely close to the same resistance)
Did you swap coils to other cylinders or just carbs ? Are you using resistance plug caps ? They can go a little wonky and get fretting or corrosion on the resistor in the plug cap changing your 5K ohm cap to 10,12,15 I have seen as high as 21k ohm in a bad cap, causes weird spark (can drastically change spark timing and intensity)
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Post by Walms on May 18, 2022 9:12:20 GMT -5
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Post by zambia on May 22, 2022 20:30:58 GMT -5
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Post by Walms on May 23, 2022 7:16:49 GMT -5
That's a weird one...
Have you pressure tested it?
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