Help! No inlet valves clearance?

Hello. I don't usually write in the forum as I find it quite hard to express myself in English.

I need your advice after searching through the forum threads and not finding an answer to my problem.

I've finnished rebuilding my 850 MkII '74 engine and when I've tried to set the inlet valve clearances I've found there was no clearance at all at any possition between the rockers and the valves.

All different parts are original and standard. No sports cam or any other thing that could get the rockers closer to the valve.
I thought I could start the engine for the weekend and finally go for a ride but seems like I'll stay in :-(

Thanks in advance.

Check that your pushrods are seated into the rockers. This is common. I have to lift the head up a bit and reset them every time I replace the head. One slips out and I expect it and resolve it. I take a look all around as I bring the head into position with the fasteners.

Did you change your cyl. base or head gasket to a thinner type? Cut new valve seats or replace any valves?

Pushrods seem to be in place...
New valves have been fitted but no seats or different gasket thickness. Got the new valves from Norvil as STD sized.
Weird ain't it?
Thanks!

Could be your old valves had been ground a time or two. Also some one at some time may have ground down your old valve stems so the new stock ones are longer but if you've backed out the adjusters all the way and the valves still don't close you need to measure the overall length of the new valves or your push rods : ( One more possibility is your old cam had been reground and longer push rods fitted.

We can't forget these are 40 year old machines and unless we've had them since new there's no telling what a previous owner has done at some time.

sparkplug said:

I've finnished rebuilding my 850 MkII '74 engine and when I've tried to set the inlet valve clearances I've found there was no clearance at all at any possition between the rockers and the valves.

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What length are the inlet pushrods?

Are 'mushroom' head rocker adjusters fitted?

Check the valve length especially if they are from a non genuine source, for a while I was buying engine components twice, first from a non genuine supplier then when parts didn't seem right I had to go buy the genuine article, expensive and it took a while to learn the lesson!
Seems strange though, at times like these you need a second pair of eyes to check there's nothing silly going on

sparkplug said:

Pushrods seem to be in place...
New valves have been fitted but no seats or different gasket thickness. Got the new valves from Norvil as STD sized.
Weird ain't it?
Thanks!

Click to expand...

Did the engine run before you took it apart? How much of the bike's history do you know?

Sure sounds like a misplaced pushrod - particularly as only one valve at issue.

Have you tried turning over engine SLOWLY to see if valves, including the one at issue, are opening and closing normally?

It's both inlet valves not closing :? This could point to longer inlet pushrods or valves if not genuine ones.

Pushrods are well fitted and the engine turns nice.

The story is: New old stock cylinders, old rh10 head (really nice and sand blasted) with new valves bought from Norvil. Pushrods are the only thing I took from a spare engine I bought but they look brill, and put them beside the old ones previous to install them to check they're the same length (did not properly meassure them).
Camshaft is an original one taken from the same engine but not the one I had on the bike as the old one was destroyed when I last had a crankshaft seizure.

Beeing the pushrods and camshaft from the same engine I'd say it's the valves length the thing to check.

I'm about to die with only the idea of having to dismantle the head again and missing this beautiful weekend ahead down here, but I guess there's no other way to know.

Thanks everybody for the good advices.

Each time valve seats are cut the valve stems come up higher. After my last valve guide replacement (the third in the bike's history), there was no clearance on two of the valves. A combination of having cut the seats and skimmed the head flat brought reduced the clearance. I had to cut down the pushrods by about .050 inch to put things back to near normal. Custom length pushrods are a more common fix than trimming valve stems. You should carefully measure your old intake pushrods against the new ones to see if they've been shortened. Sorry, but the head must come off again.

Sorry, my bad, read your message too quickly I guess.

Best of luck finding a solution!

Thank you so much buddies. You've all really helped me.

I'd like to bet the pushrods are not sitting in the cam followers correctly.

Cash

In my opinion, it is pretty hard not to get the push rods to seat on the cam followers, but it is worth a look/feel. You can unbolt the head and pull it up enough to roll the rods around and see what is going on. If you put the rods in with the barrel on the bike, you need to hold the rocker arms up high to get the push rods high enough to clear the barrel and up in the head past the rocker arms. Use rubber bands, same when putting the head on, hold the push rods up high with rubber bands and cut them off and let them fall onto the followers. Make sure with lots of light and inspection that the top of the rods are seating in the rockers before tightening, you can see all of this if you look close enough. But if the valves have been seated several times and different head and different push rods, all bets are off. It may be time to take the head off and check everything out.

Dave
69S

In my opinion, it is pretty hard not to get the push rods to seat on the cam followers,

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Yer dead right Dave but it happened to me once and boy now do I check.

Cash