Bike has very little power (120km/h high speed on highway).I compression tested both cylinders.  The left reaches 150 while the right stops at a measly 35ppi.  I have never had a valve adjustment.  Is a valve adjustment my first step or is there a quicker way to figure out the root of the problem? I'm considering simply replacing the top end(I have no garage and tinkering with the bike on the sidewalk may prove to be messy and bothersome).

Any input is appreciated.

P.S. plugs are fine, and both sides generate a spark..so I'm assuming the coils and electrical's are all fine.

Cheers!

The head would be the first thing to check. By your posts last October, you mention the problem slowly worsened. That could be a bad valve getting burnt more and more, causing you lose compression.
There could be other things, but nothing is going to be an easy quick fix.
If valves were out of adjustment and not closing, then the seats would be getting burnt. That means new valves and maybe a new head.
I think the head will have to come off to know what the real problem is. That's the only way to examine the valve seats.
If it is the rings, then the head still has to come off.

You could start with a valve adjustment and see if that helps!

Thank you!! yes I have been brushing this problem aside since last october.  Now its time to get down and do this valve adjustment.  I bought the shim tool..Time to get er done..I just hope it wont be a piston issue.  I will update!

I opened up the top end and finally checked the valve clearances. Ok so both intake valves are not in spec. However I have a little concern. As I was hand cranking the engine I had constant tension, however at one point in the turn there was zero tension. It feels like if you are pushing against a door, and then the door opens and you fall through. This happens every revolution. Any ideas?

A 4-stroke engine has 4 strokes:
Intake
Compression
Power
Exhaust

Compression is just that. Compressing air fuel mix into a small space. Resistance should be felt. Normal.

Did you take out the plugs to assist?


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Quote from: jestercinti on March 18, 2013, 08:23:13 PM
A 4-stroke engine has 4 strokes:
Intake
Compression
Power
Exhaust

Compression is just that. Compressing air fuel mix into a small space. Resistance should be felt. Normal.

Did you take out the plugs to assist?


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lol. Don't forget to take out the spark plugs!!

Update! I checked the valve clearances with my feeler gauges and both the left and right exhaust valves didn't fit my feeler gauges from 0.02-0.09..however both intakes were fine (they both fit from 0.02-0.05/0.06).  However when trying to remove both exhaust valve shims, I was unable to because the shim buckets were too tight to move around.  Does anyone know how I can take out the shims without having the valve buckets loose..I'm unable to pry out the shim.  Any help is appreciated.

One thing:  Can you turn the exhaust buckets when in position to check clearance?  If not, I expect that you will find a burnt valve.

Oh, one more thing:  Have you watched the video on checking valve clearance?

Quote from: Paulcet on March 26, 2013, 06:06:37 PM
One thing:  Can you turn the exhaust buckets when in position to check clearance?  If not, I expect that you will find a burnt valve.

Oh, one more thing:  Have you watched the video on checking valve clearance?

Firstly I have watched various videos on valve clearance checks, however none mention what to do if you can't rotate the buckets. Secondly, no I cannot turn the exhaust buckets when in position to check clearance.  reason for my dilemma.  I was expecting burnt valves anyways...question is now, what is my next step.  Do I need to remove the engine from the frame to work on the valves? Or can I just remove the camshaft?  Thanks paulcet.

You could loosen the exhaust journal caps just a little so the exhaust cam is a little loose. That can give you some room to turn the buckets and get the shims out.

You can work the whole top end without removing the engine.

If you remove the head, remember it is sort of stuck to the jugs. Lift the head and the jugs can come with it and a piston come out (don't ask how I know that, trust me I do know). You need to use a big ass screw driver and gently go around the space bwteen the jugs and the head to get the head loose from the jugs. Then you can take the head off. 2 people always work better: one can yell STOP while the jugs come up because you can't see that while lifting up the head.

Well, they don't mention what to do if you can't rotate the buckets because that should never happen.  I would remove the head.  I suppose you could roll the dice if you don't mind the extra work and pull the cam shaft to replace the shims.  Be very careful with the cam caps. 

You don't need to remove the engine from the frame to remove the head or cylinders.

Ok so what should I do first. loosen the exhaust journal caps, then change the shims to spec to see if it fixes anything?.Then if that doesn't fix anything I can take off the top end?

How would I go about loosening the cam caps?Would I need to remove the cam chain tensioner to do this? Do there happen to be any tutorials around youtube?

Thanks guys

You need a wrench - 12 or 14mm - to loosen them just a couple turns. just enough to turn the shim buckets. No need to loosen anything else. All you need is for them to have maybe 0.1mm space to turn the buckets.
When the shims are out, put in much thinner shims and tighten back down.
Now you should be able to do a valve adjustment by the book.

Wait, so you are saying that I need to put in much smaller shims, tighten it back down.  Then I need to do the valve adjustment and put in another set of shims..Meaning 4 shims for the 2 exhaust valves??

Quote from: junk301 on March 26, 2013, 11:16:12 PM
Wait, so you are saying that I need to put in much smaller shims, tighten it back down.  Then I need to do the valve adjustment and put in another set of shims..Meaning 4 shims for the 2 exhaust valves??

Basically yes. You need a set of shims in there to get a reading so you know if it needs adjusting. Since your valves are so tight and you can not get a reading at the moment you need to put a set of much thinner shims in than the ones that you will remove and recheck your clearances to see where you are at.

Ok great...how much thinner should I go? 10-15? Btw there wasn't even 0.02mm clearance. I need to get this done fast. Will update after new shims are in.

I would try .10 as a start. 

as in 2.10? that low??

Quote from: snOhio on March 27, 2013, 04:40:43 PM
a test shim will let you figure out exactly what you need to order.  that way, instead of stepping down .05 and realizing you should have gone down .1, you can get it right the first time.

Yes, that was exactly my worry since I have to go and order the shims..Btw what exactly are test shims..do you happen to know where I can order them?