valve clearances

[chaz]

did the clearances back in March, around July put new auto CCT's in.

just rechecked clearances as bike now wont start.
front exhaust are 0.3 rear exhaust are 0.28
both front and rear inlets are less than 0.05 probably 0.025 or less so around zero to a thou.

any reason gaps are closed up on inlets so much?
not looking forward to doing them again so soon as this and probably only done 3000 max miles since

[sirch345]

This is a bit of a strange one to me, on why the gaps would close up

Any ideas anyone

Chris.

[lloydie]

This is a bit of a strange one to me, on why the gaps would close up

Any ideas anyone

Chris.

Because they wasn't set right the previous Time me thinks .

[chaz]

were set right back in march, bike had been running ok, only thing changed was ccts, cant see why only the inlets tightened up. surely if they had been set wrong they wouldn't both be same on both cam lobes and cams, as I said both inlets are same and both exhausts are near the same.
dosnt front cct run on inlet side and rear run on exhaust side of chain?

[sirch345]

This is a bit of a strange one to me, on why the gaps would close up

Any ideas anyone

Chris.

Because they wasn't set right the previous Time me thinks .

that was the only answer I could come up with, but knowing Chaz is normally very thorough, it didn't ought to be that

Chris.

[tony.mon]

Yes, they are front CCT on the inlet side and rear on the exhaust side.

Is the engine set in the correct place to measure the clearances, with the RT or FT mark lined up?
If so:


There's only a few ways that the clearances can close up.
Either
1. the cam has moved closer to the head of the valve, or
2. the head of the valve has moved closer to the cam.

How could 1. occur?
If the cam chain tension was set too tight the cam could have worn into the head. This could also occur because insufficient oil was reaching the bearing journal surface.

How could 2. occur? If the valve seats wear the valve sits in to the head, it's more recessed, if you like- this has the effect of closing up the clearances.

You now have two options.
You could just rest the clearances and see how it goes.
Or you could pull one or both heads and inspect.

The first option is easier- but before doing so just look at the cam journal surface for signs of scoring, and, on the rear head particularly, it's the work of a few minutes to pull the cams out and inspect the journal seat.

Suggest you do that first, remembering to set the engine in the right position first.

[chaz]

thanks Tony, being honest Ive done a few cct changes and valve clearances as I was running a bike shop for the last 8 years, while also working in engineering , but since a bike accident in April I have problems getting in positions twisting back and neck. this aggrevating the neck problems after my cancer operations.. sh!t couple of years.
I did the clearances back in march and still have the original shims and workings where it shows I took out the same as I need to take out again.
I couldn't get the centre crank cap out , so used the back wheel method to turn the motor I don't think there was a problem lining up as I checked cam markings as well.
bike ran ok for 8 months but the last 2 weeks it hasn't wanted to start.
Ive now chiselled the cap out so easier to turn over. Ive now got the shims out and as said above, to open up I have to take the same off 0.16 as did last time I did them.
will check cam bearing surfaces tomorrow , then get more shims.

[tony.mon]

Trouble is, running on zero/less than zero clearances will mean that the valves aren't seated which allows hot gases to leak past the seat, eroding the seat and/or valve.

Have you checked compression?

[chaz]

Tony, couldn't test compression as too deep for my normal tester, my other is a pain as you have to join pipes and its a bit stiff on the front pot..
in bits at moment so waiting for shims to come.

[tony.mon]

I'm concerned over this.
These engines don't move much as regards clearances, normally even after 20k miles between checks most are still within tolerance. Any that are out tend to be only. 05 out.
The rate yours seem to be changing indicates that there is something awry.

Honda valve seats are good and hard, and don't wear much even though you no longer have lead in fuel to keep them lubed.

[sirch345]

I'm concerned over this.
These engines don't move much as regards clearances, normally even after 20k miles between checks most are still within tolerance. Any that are out tend to be only. 05 out.
The rate yours seem to be changing indicates that there is something awry.

Honda valve seats are good and hard, and don't wear much even though you no longer have lead in fuel to keep them lubed.

That has been my thoughts on this, something is just not adding up here. What makes it more puzzling is that it's happening to both front and rear inlet cams.

Checking the camshaft journals as Tony suggests in one of his posts above sounds like a good plan to start with.

Out of interest, is the bike more or less standard as far as you can tell in the engine department

Chris.

[chaz]

going to check cams at weekend.
as far as I know bike is standard apart from Scorpion cans. Ive looked after it since the lad bought it , but he got it from Budget Bikes in Swindon... maybe the clue is in the name where he got it from

[Seeker 77]

but he got it from Budget Bikes in Swindon... maybe the clue is in the name where he got it from

Always a chance that you have picked up a lemon, but I've had two unbelievably high mileage K5 GSXR 1000s from them and both were spot on.