GS750, tight spot when hand cranked.

[bob654]

Hi, thanks in advance. I am rebuilding my bike after getting the head skimmed, 9 thou. Got as far as putting the rebuilt head back on the bike today, put the cams back on and bolted down, replaced the pully wheel. 

I turned over by hand a few times today before stopping, (limited to daylight work,) and there seems to be a tight lobe, Its always the same spot on the cycle. Exhaust, number 1 cylinder. 

I wonder where to start in the morning? Check the shim? Is it normal to have a spot that is tighter?

[TonyGee]

check the valve clearance first, then check cam timing. 

[bob654]

Cheers, will do. The head skim shouldn't effect the valve clearance, eh? I  checked the cam timing about 10 times today, so will check again. That only leaves, me mixing my shims, when they were off., and I didnt think I did? Oh well fresh start in the morning.

[bob654]

I will check all my buckets are moving too.

 

[Swiss Toni]

The old habit of making sure everything turns nicely at each stage of a rebuild, makes it a lot easier to locate the cause of said 'stiction'!

[bob654]

Would not, having the cam chain tensioner installed  have anything to do with this?

 

[TonyGee]

18 minutes ago, bob654 said:

Would not, having the cam chain tensioner installed  have anything to do with this?

 

you don't want to turn an engine over with no tensioner fitted 

[bob654]

Just hand turn so far.

[TonyGee]

5 minutes ago, bob654 said:

Just hand turn so far.

no !!!  never turn the crank till the tensioner is fitted and the cam timing is checked. 

[bob654]

Right, had another go this morning. Tensioner installed, first, checked the timing and I was off one cog between cams. Now she turns smoothly all the way round.

Thank you.

[denisd]

Happy days 

[TLRS]

19 hours ago, TonyGee said:

no !!!  never turn the crank till the tensioner is fitted and the cam timing is checked. 

Go on, spill the beans?

Will there be enough play in the timing that pistons could hit valves without a pensioner?

[Gixer1460]

1 hour ago, TLRS said:

Go on, spill the beans?

Will there be enough play in the timing that pistons could hit valves without a pensioner?

Without the chain being tensioned, there is the easy possibility of the chain skipping a tooth - as seems to have happened here!

[cnap504]

4 hours ago, Gixer1460 said:

Without the chain being tensioned, there is the easy possibility of the chain skipping a tooth - as seems to have happened here!

Yep^^  so when it’s running might be a good idea to do a compression test