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Won't start. Very low compression. 8 years 7 months ago #8484

  • Ledkz1300
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Well, I managed to get the starter clutch fixed by calling in a professional. Starter works great but now it won't start.

Lots of spark, didn't seem like it was getting any fuel. Did a compression check and I just about cried.

115/115/90/70/75/115

So the faq says it probably won't start if the compression is that low. Thing is, other than the starter clutch being bad I've been starting and running it with no trouble at all for the last couple of weeks. It usually starts faster than you can get the button on and off.

I don't know what to do now.

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Won't start. Very low compression. 8 years 7 months ago #8485

  • Lucien-Harpress
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You didn't happen to hydrolock it, did you?

Other options are sticky valves and stuck rings, but both are unlikely if you've been running it. When you ran it before, are you sure it was running on all 6 cylinders? These things will idle deceptively smooth on less than 6, and problems will really only show up on an actual ride. Might have been a problem that was already there, but easily missed until now.

First off, check your valve clearances. Then, dump some oil down the spark plug holes of the bad cylinders to see if the numbers come up (would be bad rings if the do). If none of this works..... you may have to dig deeper.

I recall you having starting issues- this wouldn't have been motor issues, having difficulty turning over, would it? Did you ever leave the petcock on?

Really sucks to hear. Still, take 5, walk away a bit, come back later, and start with the easy stuff. The hard stuff can come later, if need be.

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Last edit: by Lucien-Harpress.

Won't start. Very low compression. 8 years 7 months ago #8486

  • Kawboy
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A leak down check will tell you exactly where the problem is. In lieu of that since you don't have the tool (and I'll assume that because if you had one you'd know what to do)

Check your valve clearances especially the exhaust. You have compression but it's low. possibly tight valves. Next, you have 2 adjacent cylinders that are low. There is a possibility that the head gasket is leaking in between the 2 cylinders. Rare, but possible.

All the readings are low but you tell us that it won't start, so again I'll assume the engine is cold. Not the ideal time to do compression testing, so don't get upset yet. I would expect to see low readings on a cold engine.

You have enough compression to initiate a start. I've seen lots of engines start with 80 psi in all cylinders. If you have atomized gas, air and spark, it will go, so something is definitely off.

Go have a coffee or go for a walk and clear your head. Now's not the time to get in to it. Walk away and come back another day. All will become clear. I can't count how many times I've done this and it's paid off. Patience is the key and when you figured it out, you'll have a laugh about it.

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Won't start. Very low compression. 8 years 7 months ago #8487

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Lucien makes a good point about the petcock. He would know. Pretty sure he just replaced a couple of bent connecting rods. So lets think positive thoughts until proven otherwise.

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Won't start. Very low compression. 8 years 7 months ago #8489

  • Ledkz1300
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Thanks guys.

I don't know what the symptoms of a hydrolock are but its possible?

I've never left the gas on but I've only owned it for less than a month. Who knows what the previous owner did but he did lots of other stuff, starting with not taking even basic care of it. The PO put an inline gas valve which I dutifully shut off every time I finish riding.

I'm fairly certain its been running on all six. Under 3000 RPM no.... over 3000 RPM I'd say yes. Smooth power from 3000 up and it really wakes up over 5000. The plugs are all burning a nice brown and no wet or black ones. It doesn't idle, and misses a lot when it first starts for a few seconds. Then as the engine runs for a few the other missing cylinders start to fire as the RPM come up. Doesn't look or smell like its burning oil.

It has never had difficulty turning it over and starting, with the exception of the starter clutch slipping out, and the starter switch itself. Turns 2 or 3 times and starts right up.

Yes, the compression test was done on a cold engine. We did it because it wasn't starting but I was wrong on one of the numbers... 70 should read 30 so worse than I thought on that cylinder.

He dropped some oil down inside and did the test a second time with no real changes in the numbers.

He doesn't have a leak down tester.

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Won't start. Very low compression. 8 years 7 months ago #8496

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30 is really low. I would suspect a bent valve or burnt valve. Even at cranking rpm you should be better than 30. Definitely check the valve clearances. a really tight valve might come up at 30. Fingers crossed.

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