smart51
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| posted on 24/9/08 at 06:51 PM |
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R1 engine trouble. Help me diagnose it please - fixed
I've just had a nice track day at Silverstone. The engine behaved beautifully throughout. It was driven hard but with some sympathy and gave
no hint of any problem.
Then I packed up to go home. The engine worked smoothly and sweetly as usual when idling, when cruising at a steady speed and when accelerating very
gently. With any increase in throttle the engine was rough and whilst it would rev, I took it very gently home.
At home I looked at the spark plugs. No 1 and No 2 were a little black and crusty but dry. A bit rich perhaps. No 3 was good. No 4 was a bit oily.
Fresh oil, not the black sticky mess in the Haynes manual. It looked OK but my fingers were oily afterwards.
Next I did a compression test. 120 PSI in all cylinders +/- 5 PSI. Nice and even but very low.
The big ends went 18 months ago and I replaced them all. It sounded bad at idle and worse with any revs. This sounds very sweet at tickover, fast
idle and at a 30 MPH cruise. It sounded fine high higher steady speeds through my crash helmet too.
What can the matter be?
[Edited on 26-9-2008 by smart51]
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Mark G
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| posted on 24/9/08 at 07:02 PM |
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Does it misfire atall? what made you think it was plugs?
Its obviously hard to tell from a description but it really could be anything from fuel starvation to a loose manifold...
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MkIndy7
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| posted on 24/9/08 at 07:09 PM |
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Did you have the throttle open when doing the compression test?
That gives consistantly low readings over all cylinders.
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smart51
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| posted on 24/9/08 at 07:20 PM |
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quote:
Originally posted by MkIndy7
Did you have the throttle open when doing the compression test?
That gives consistantly low readings over all cylinders.
No. Oops. That's one to retry.
As for the plugs, start at the top and work down. The engine was very lumpy and woudn't pull well with any throttle so I thought it might not
be running on all cylinders. I don't know what that feels like so I just tried it.
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BenB
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| posted on 24/9/08 at 09:31 PM |
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Has the noise changed? I had something like this and it turned out to be a leaking exhaust gasket......
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smart51
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| posted on 25/9/08 at 07:32 AM |
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quote:
Originally posted by BenB
Has the noise changed? I had something like this and it turned out to be a leaking exhaust gasket......
The noise is different if you have a bit of throttle on. I've put my hand round the exhaust manifold and there doesn't seem to be a leak.
TBH the engine feels so bad with a bit of throttle that I wouldn't think a gasket leak could be the cause.
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mad-butcher
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| posted on 25/9/08 at 08:00 AM |
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not something simple like a couple off loosw main jets
tony
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ragindave
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| posted on 25/9/08 at 08:29 AM |
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Change the spark plugs first sounds like you may have a mis fire.
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ragindave
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| posted on 25/9/08 at 08:30 AM |
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Change the oily spark plug this is a good indication that that is the one not working
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smart51
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| posted on 25/9/08 at 08:26 PM |
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Well I was thinking about this today. It ran beautifully at small throttle openings but badly from 1/4 throttle up so perhaps its fuelling, since the
idle circuit feeds low throttle and the main / needle the rest.
The main jets are all OK but I noticed one of the air jets that was blocked up now isn't. I also did a compression test with wide open throttle
but with a cold engine. 175 PSI in 2 cylinders, 170 in no 3 and 160 in no 4. More or less OK.
Baby duties called after that but tomorrow I'll do a test drive. HOPEFULLY, that will be it but I think that the engine symptoms were much
worse than an unblocked air jet on 1 cylinder could make.
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smart51
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| posted on 26/9/08 at 01:29 PM |
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Well that seems to have fixed it. It was the blob of silicone blocking up the air jet falling off that was the cause. I have to say, it was
terrible. A nice easy fix too.
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mad-butcher
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| posted on 26/9/08 at 04:14 PM |
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can you not solder/silver solder up the hole in the jet to cure it once and for all
Tony
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Coose
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| posted on 26/9/08 at 10:00 PM |
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quote:
Originally posted by mad-butcher
can you not solder/silver solder up the hole in the jet to cure it once and for all
Tony
Doubtful as it's a sod to get to. JB Weld putty and a matchstick are your friends.... 
Spin 'er off Well...
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