Ok Guys no compression on front cylinder
11-26-2011, 06:17 PM
#1
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Squid
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Location: Cottotown,Tn.
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Ok Guys no compression on front cylinder
OK i installed kreiger mccts timing all checked ok ,put back together and it only ran on rear cylinder. I did a compression test and had 150 psi on the rear and 0 on the front . I pulled the head off and no bent valves but I had a ton of soft carbon on the head and top of piston. I was thinking of pulling front piston ,thought maybe rings are carboned closed or cylinder gas washed not getting a good seal. I am going to send head out to get cleaned and checked . Any other sugeestions would be greatly appreciated . I guess i need to go thru carbs while off the bike .
11-26-2011, 06:59 PM
#2
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SuperSport
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Was there any problem before the CCT change? I know you said it checked out, but if that was the only thing you tinkered with, what else could it be?
Even if it was the rings I'd expect to see SOME compression. Not zero.
Even if it was the rings I'd expect to see SOME compression. Not zero.
11-26-2011, 08:10 PM
#7
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Stuck rings are only going to give you low compression. Hopefully your cam timing is off. I just hope that you didn't bend the valves. They can appear to be seated, but bent. Did you see any signs of piston to valve contact on the top of the piston?
11-26-2011, 09:02 PM
#9
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Superstock
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Check your tools too.
It's very challenging to get zero compression out of an engine.
If you didn't hear any crunchy noises when you started cranking the engine then you shouldn't have done any damage but places to check are valve clearances
11-26-2011, 09:36 PM
#10
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Never tried WD. I've always used brake cleaner. I figured WD would be to thick to get through if you have a bad valve instead of a bent one. If it's not sealing and you check with brake cleaner, it'll leave a wet spot.
11-26-2011, 09:53 PM
#11
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MotoGP
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Once again, it truly seems that just as many VTR's loose there engine due to failed MCCT installation as they do due to failed factory CCT's.
You also should have checked the valve clearances before you removed the head. That would tell you right away if any valves were bent (the clearances would have opened up)
Also it really isn't a good idea to only service one head. The other one will look the same, so you might as well have them both done.
As a FYI the reason for all the carbon build up is the engine is never rev'd.
Run a 4 valve engine at low RPM all the time and that is the result. You need to go and blow the gunk out from time to time. Twist the throttle and let it see some rev's and you won't have the carbon problem.
You also should have checked the valve clearances before you removed the head. That would tell you right away if any valves were bent (the clearances would have opened up)
Also it really isn't a good idea to only service one head. The other one will look the same, so you might as well have them both done.
As a FYI the reason for all the carbon build up is the engine is never rev'd.
Run a 4 valve engine at low RPM all the time and that is the result. You need to go and blow the gunk out from time to time. Twist the throttle and let it see some rev's and you won't have the carbon problem.
11-27-2011, 01:51 AM
#12
aka tony.mon, vtr1000.org
Squid
Join Date: Mar 2009
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With the front head, if replaced in situ, it's possible to unseat the head gasket as you drop the head into place.
This could explain the problem, but like the others I'm unsure as to why there NO pressure- did you try the gauge back on the rear one, to make sure it sin't a gauge fault?
This could explain the problem, but like the others I'm unsure as to why there NO pressure- did you try the gauge back on the rear one, to make sure it sin't a gauge fault?
11-27-2011, 06:28 AM
#13
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Squid
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Ok i appreciate all the responses , i have only had the bike about 6 weeks when this happened . i am removing rear cylinder head also appears soft carbon is holdingthe intake valves open slightly. and yes i checked the rear cylinder compression was 150 there.
12-24-2011, 07:36 PM
#17
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SuperBike
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I had a soft carbon issue from a bike running too rich. Problem was a choke cable out of place and the chokes couldn't close. Get rid of the carbon and all should be fine. Rings can be pretty carboned up as well. Make sure you check the valves for any bends, which is easy to do once out of the head. roll the stem on a flat surface and watch the head of the valve. If you can't pull them apart, check for a leak on the seat with fluid. Any questions, just ask.
12-24-2011, 11:03 PM
#18
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I've done it for years, never had a problem with brake cleaner wicking up the valve stem and destroying the seal. YMMV. But brake cleaner is not much of a different solvent than gas. So you'd think gas would destroy them as well. And there is gas in the oil. Most valve guide seals IIRC are made of nitrile (not sure on the spelling). And Nitrile is pretty impervious to most chemicals.
12-25-2011, 09:43 AM
#19
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Brake clean WILL ruin rubber. It is nothing like gas as it is not petroleum based. It probably won't hurt for doing a simple leak test, but spray an extra o ring with brake cleaner and let it sit for a day, it will be dried out and ready to crack.
12-25-2011, 09:45 AM
#20
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It's even worse on plastic, it can be used for cleaning but special care needs to be taken.
(my experience is I have been professionally detailing cars for 2 years now and we use brake clean on a daily basis. It's great, but you need to be very careful)
(my experience is I have been professionally detailing cars for 2 years now and we use brake clean on a daily basis. It's great, but you need to be very careful)
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