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Post by hunleysfriend on Mar 28, 2018 8:43:12 GMT -5
New issue with same KH400. Spark problem addressed. Clogged jet sorted. Bike was out on a rare sunny day this time of year and after a pretty normal albeit short putt up the road and back (6 or 7 miles total) the engine died. Not like it was shut off but as if one cyl after another quickly quit.
Back to researching. Collective wisdom on this site had me check gas cap vent, fuel flow, spark and COMPRESSION.
175 psi with no more than 10% difference between each pot is correct. Bike can run happily on 125 psi. Got it.
Mine has 100 psi when tested cold. Throttle WO. That’s all three cyl. Within a psi or 2. It will still fire up from cold but doesn’t seem to want to stay running. Reading here indicates the compression reading will only go down with heat anyway so.....
can an engine run with 100 psi compression or is my gauge NG?
If it can, I’m looking at a top end rebuild I’m guessing?
Btw I want to again thank you lads for the help & encouragement.
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Post by JA-Moo on Mar 28, 2018 11:04:21 GMT -5
Stock compression is 150-155psi. It should "run" with a 100, but pretty weak. It is always good to check wiht another compression tester to verify. Are you holding the throttle WFO land kicking like a crazy man until the gauge stops going up?
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Post by hunleysfriend on Mar 28, 2018 16:58:01 GMT -5
Yes and yes. I've got another tester but it's a two man affair. Kicked like crazy to get it to 100.
I'd have thought as low as the reading was it shouldn't even light, yet it starts every time. Just won't stay running.
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Post by Curtis on Mar 28, 2018 17:33:11 GMT -5
How long is the hose on the compression tester?
You need to take into account that a long hose (no giggity) will lower the compression reading since you are adding more volume to the cylinder
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Post by reimair on Mar 28, 2018 19:01:47 GMT -5
As far as quitting all 3 like that after sitting for a bit. Most likely fuel shortage or not charging. Check your voltage and flow from the valve. If it ran to start with and didn't seize, Compression is not likely the problem.
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Post by Curtis on Mar 28, 2018 19:05:04 GMT -5
Re reading your post I am going to be suspect of a fuel issue
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Post by hunleysfriend on Mar 29, 2018 13:48:54 GMT -5
I'm rebuilding the carbs. New petcock and hoses. Fuel flowing to carbs. Let me get these carbs rebuilt and I'll be back.
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Post by hunleysfriend on Mar 29, 2018 14:04:46 GMT -5
The hose is about 16 inches long. Will that really cause a low reading? I figured it would pump up to a set value regardless.
Must try that other gauge.
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Post by Curtis on Mar 29, 2018 18:49:43 GMT -5
It depends where the bleeder is for the compression tester. The closer the gauge the more cylinder volume you will have - the closer the the spark plug hole the more accurate the reading will be
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Post by JA-Moo on Mar 29, 2018 21:33:43 GMT -5
It will be ok if it has a shrader in the fitting that screws into the head.
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Post by Curtis on Mar 29, 2018 21:41:42 GMT -5
It will be ok if it has a shrader in the fitting that screws into the head. Sooooooo, Just what I said eh Johnny boy |
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Post by JA-Moo on Mar 30, 2018 9:24:13 GMT -5
It will be ok if it has a shrader in the fitting that screws into the head. Sooooooo, Just what I said eh Johnny boy Kinda sorta.....lol. Your statement was correct, But I have seen testers with the shraders all over the length of the tube/s. The only place where the hose volume is not a factor is when the bottom shrader is in the end where it screws in. |
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Post by hunleysfriend on Apr 11, 2018 19:13:40 GMT -5
Low speed coil fried. Replaced with OEM. Tough soldering but done. Bike runs great now. So good in fact the clutch slips. Looking to order some friction plates and springs from EBC. If it’s not one thing it’s another. I’m not gonna fuss about the compression readings.
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Post by Walms on Apr 12, 2018 3:39:43 GMT -5
A slipping clutch can be a positive thing! There are a few things to check before buying new fibres, first is to make sure the clutch basket spring cover is aligned properly looking at the alignment notches. Make sure the steel plates are flat (lap them on a flat surface and look for contact)
I just mention these because I got bit by both when I replaced the fibres thinking that would solve it.
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Post by hunleysfriend on Apr 12, 2018 21:32:30 GMT -5
Thanx Walms, I’ll check. BTW the bike I’m working on is still on youtube. youtu.be/Bi8hQ1OU4xYIt was that video which sold me on buying the bike. |
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