Kawi2strokes.com Forum

So, my h2 starts up and seems to run pretty well but I noticed that the left cylinder seems to not be firing too well at idle. I pulled the carb and cleaned it out, it had a little bit of junk in the bowl. After reinstalling it seemed to be running a bit better, but I still wonder if I have an air leak at the boot. Some more info:

-the boot doesn't seem to clamp down on the carb nearly as tightly as the other two do. I can't spin the center and right cyl carbs in the boots, but I can the left one (it won't slip due to vibration but a not too hefty twist of the hand will definately move it)

-the left cylinder seems to have an excessive amount of piston rattle. I checked the plug for good spark and it has it. I also checked the ignition timing and it seems to be right on at 4000 rpm (note: I only have a timing light so I could not set the piston to the proper degrees BTDC). Additionally, I checked compression and it has a nice, robust 145 psi. Seems like if there was a lot of slop in the cylinder that the compression would be down....?

-I synched my carbs using a set of vacuum gages and I had to lift the slide on the left carb significantly more to get the same vacuum reading as the other two (maybe 1.5 millimeter more)

-I haven't been able to get out and ride it long enough to get a plug reading

I'm hoping that my rattle and vacuum problems are just due to a bad boot (cheaper than a piston!)

thanks for any input offered!

jason

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ride hard, ride long, ride safe!
Jason
72 h2 in a 93 Katana
03 cbr600rr
80 kz750 ltd
94 pw50

Just out of curiosity...if you tweak the slide up or down slightly on the offending carb, does the rattle go away? Also does it disappear when the engine is fully up to temperature?

Sounds like an inlet leak. With the engine running, spray starting fluid directly on the carb boots. When the engine revs up you have found your leak.

Good luck.

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Rotortech
Indianapolis
1974 S3

zambia
droppin the slide more causes the rattle to get worse....
I don't know that the rattle goes away when the engine reaches full temp either. I let it idle in the garage for quite a while today (20 min or so) and it never went away. Spraying carb cleaner on the exhaust pipe resulted in the fluid evaporating immediately, so I think it was warmed up pretty well

I forgot to mention in my original post that I did try to find any leaks using carb cleaner. i never go the rpm's to jump up. they actually dropped a little when I sprayed cleaner on the offending boot. I thought that was wierd, so I sprayed a little on the intake filter for that carb and the rpm's dropped when I did that too. that's a little different than usual, but I found it intriguing that rpm's dropped when spraying fluid on the filter and also on the boot. Seems to point to a minor leak to me...

_________________
ride hard, ride long, ride safe!
Jason
72 h2 in a 93 Katana
03 cbr600rr
80 kz750 ltd
94 pw50

Not to try to stop you from trying to find the problem, but rattling pistons are anything but unusual for triples. My right piston is starting to get louder than the exhaust.

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If it surges, that's normal, upshift.

Pretty much with Jim on this one, I think experience gives you a baseline on H2 piston rattle. They can get noisy with no detrimental effect, but I guess if you've got two quiet ones............ well, that is unusual! I don't think an air-leak at idle will cause piston rattle, by itself. Back in the day I had a 50,000 mile plus H2 on original pistons - Man, that thing rattled, but it was fast!

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"One day, your life will flash before your eyes. Make sure it's worth watching." : anon.

jason - grab a can of starter fluid and re-do that test. I think the revs will jump. It sure sounds to me like you have a leak. A tiny leak can really make a big difference.

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Rotortech
Indianapolis
1974 S3

It seems the carb sync is good so the culprit could well be timing. When I set static timing on my points bikes I am always surprised to see how far off an engine can be and still run OK. if the timing is a few degrees out, the piston can rattle. If air leak is the problem you should have other symptoms, such as a very slow return to idle after blipping the throttle. The other guys are right too though -- some of these things just flat out rattle I find the rattle subsides with heat and almost goes completely away when you're riding under load. But in any case, if there is even a small possibility the timing is out...it needs to be dealt with.

Not to sound like a smart but at our shop I work on a lot of diesels and starting fluid is like forbidden fruit as it dries out the cylinders wouldn't it be wiser to use something like carb cleaner.

Most of the decent starter fluids have "upper cylinder lubricant" in the formula.
I think that if the triple is running, a spray won't wash out anything that won't be re-introduced in the next piston cycle.

Does anyone have any short term fixes for the cracked boots? 3M black urethane?
I remember trying to find a set that cost less than 5 gold bars, and a liver, and was in stock.

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'72 H2 : Blue-ish.