valve guides

[ogre]

hi all just sorted my cb750 1970 barrels and head my local cylinder head place rebored my barrels they seem good now fitting new pistons and rings .25 oversize and i checked the play to the manual of my valves in the guides the manual says .08mm to .1 but i got .15mm so i changed the guides pig to fit but managed it took it to the head guys they reamed them an recut them got it back and i have the same play in them .15 as before spoke to them they assure me that this is the play they give all aircooled motorcycle heads are they right or am i heading for disaster cos don't want to take engine out again if its burns oil cos of this. 

[Tomb]

I have reamed out new fitted home made valve guides in my old Triumph head, I did them about two thou clearance or 0.05mm, I seem to remember this is the recommended clearance in the factory Triumph manual.

0.15mm does seem a big clearance, but there again so does the manual size of 0.10mm

As for burning oil? if you renew the guide seals it shouldn't but not sure how long they'd last with big clearance on the valve stems

[Seamus]

1970 K1 only has seals on one side, so not sure if this will work. Last ones I had done were reamed out to suit the valves. each guide was slightly different. i guess you really have no choice but to go with what you have. Best bet is to tell the machine shop what tolerance you want.
Unfortunately hindsight, but I believe Honda tolerances were a bit less than other makes.

[ogre]

youre right but i did tell them it needed to be 6.6 as per spec but they know best i turned down a piece of bar tonight at work as a test piece to 6.61mm to be fair its a snug fit in the exhaust guides with no seals but it pisses in the inlet guides i tried it in my old inlet guides and is a snug fit wish i hadn't of changed them now but there was movement on the valves when i tested them and the valves measured right do you reckon i could put the old guides back in

[UK Pete]

IT might seem harsh but i would get new guides and have them installed properly  and  to the tolerence i ask for by a better firm, it will mean having to recut the seats but just think how pissed you would be having to take engine back out tear it down , buy a new gasket set etc , now is the time to bite the bullet and get it done right and put it down to experience
I had a reputable firm ( stan stevens) do me a rebore many years back i gave them the barrel and new piston told them the tolerence, they did the same thing and made the bore tolerence bigger as they new best, the result was my pistons ring end gaps were beyond what yamaha stated as maximum , the bike smoked when put back together and was probably worse than it was when i gave it to them, i then had to get my barrel re sleeved by SIP  and rebuild the top end again, if this sort of thing ever happens to me again i will be looking to get even rather than swallowing the loss as a bad experience
pete

[Bryanj]

Refit new guides and get a honda dealer with the correct reamer to ream them then take it to a head shop for the seats to be re-cut