Problem: The bike has become hard to start with cold engine, and it has to be warmed up couple of minutes before it starts to idle. After the engine is warmed up, the bike works perfectly.

I took the carbs of and cleaned them thoroughly and checked that the choke operate correclty; no effect. Then I've checked the valve clearance, exhaust valves were all between 0,2..0,25mm but I only managed to get the smallest wheeler (0,05mm) between one intake valve lifter and camshaft! The other 7's clearances were <0,05mm. Problem found, I think.

- Does it harm the bike, if I ride it without any clearance on intake valve(s)? Ex valves burn easily, but how 'bout intake valves? The bike works perfectly after about two or three minutes warming up with 2-3kRPM.

- Can the valves be adjusted with the engine mounted to bike?

- Acc. to the previous owner, the valves were adjusted max 25tkm ago. If it's so, is it normal that the intake valve clearance dissappear after 25tkm or should I prepare myself to bigger project here?

 

Yes - it can be done with the motor in the bike - but you'll need all lower fairings off, radiator removed or moved out of the way. Not 100% sure if you need to pull the tank and airbox assembly - but might not hurt.

The Honda manual says the intake clearance should be 0.16(+/_ 0.03mm).

One thing though - were you rotating the motor when measuring your intake valves? It seems that you were measuring your exhaust valves with the motor 180* to where you should be measuring the Intake valves.

 

I rotated the engine so the tip of the cam always pointed up on the cyl and valve i was measuring.

 

hmm - honestly, I haven't checked my valve clearances yet, just read the procedures through. you definitely don't check all valves with the cams in the same position.

Start off by pulling the pulse rotor cover off & rotating the pulse rotor clockwise and lining the T-mark on the pulse rotor up with the index mark on the rotor cover. At this point your cam gears should have the "In" and "Ex" marks opposing each other, and they should be level with the edge of the cyl head upper surface. If those 2 marks are next to each other on the gears, you need to turn the crank over another 360* clockwise.

At this point you need to pull the CCT. Then measure the intake valve clearance on Cyls # 1&3. Should be 0.16 as mentioned above.

Then turn the crankshaft 1/2 turn (180*) - the Index line on the Pluse Generator should be pointing straight up. Check Cyl 2 & 4 Exhaust valve clearance in this position.

Crankshaft clockwise another 180* and line the T-mark back up with the mark on the cover again. Check #2 & 4 cyl intake valves in this position.

Another half turn and check the #1 & 3 cyls Exhaust valve here.

I'm curious if the positioning and order get you different results than you got before.

 

I meant that I rotate the engine -> check the valves with cams facing away, then rotate the engine more and check another valves etc. Of course U need to rotate the engine while checking.

 

The way that you're checking is fine. The manual describes a specific proceedure which provides for the least amount of turning of the crank to make all the checks. So long as the lobes of the cams are pointing directly away from the lifters, then you're fine. You would be checking at the lowest point on the cams. You need to make sure that your engine has cooled for 12 to 24 hours before making your checks. A warm engine will make your measurements inacurate.

As for not being able to get the 0.05mm feeler under the cams on 7 of them doesn't mean that they are 0.00, but it certainly means they're not within spec. To make the adjustments, you need to get another gauge that has smaller feelers so that you can determine exactly what the gap currently is. Only with that information can you determine what size shim you'll need to install based on what shim is currently in there. You have to remove the cam shafts in order to change the shims. All of this work can be done with the engine in the frame.

On a side note, the reason it probably runs ok after it warms up is because the valve clearance actually increases on these aluminum engines. The aluminum heads expand at a higher rate than the steel valves do. This causes the valves to actually be moved further away from the cams.

 

Thanks for the info. Do you (or anybody else) have any idea is it harmfull to the engine to drive the bike, assuming that at least one intake valve hasn't got any clearance at all? Or should those be adjusted immediately?

 

I would recommend checking and adjusting as soon as you can.

 

Finally had some time for my bike, and managed to adjust the intake valves. It wasn't as big deal as I expected. The bike feels like a new now, it starts instantly with cold engine and I think it has more power and torque also.

 

Well, the only thing left to do now is get out there and ride that bike. Enjoy...