I am installing a 47mm bbk on a new engine before putting the engine on my scooter. My issue is valve adjustments. The kit came with a new head, and after I installed the cam and rocker, I can't get the adjustment close enough for good clearance. I'm aiming for. 004 on both intake and exhaust, but I run out of threads for the locking nut at about. 007/.008. Just use the old head? Or longer adjustment screw, if they exist? What do you guys think?
Post by Scooters To Go on Oct 5, 2020 9:38:57 GMT -5
Hi Josh, Did you get a new cam holder with the kit? It sounds like you have a 64mm valve length head and a 69mm cam holder. Check the engine stamp on the casing above the variator to see if it is a 139qmb or a p139qmb. If it is a “p” then you have a 69mm cam holder that won’t match your new head.
Scooters To GO
Affordable Sales, Service, and Performance
744 36th St SW
Wyoming, MI 49509
I don't think the kit came with a new cam holder, if it did I overlooked it. I'll look into that. Sounds like that's the issue, because I just put the old one on. (Original 49cc cam holder on the bbk) So that's probably it. I'd rather get the new cam holder than use the original cylinder head to make it work.
The rocker arms/cam followers are different between the two lengths. The shorter valve stem does not protrude at all above the gasket surface of the cover. I think the springs on 64mm valves do stick up just a little above the machined gasket surface. If you use the incorrect carrier/rockers, the short ones won't reach, or will be too long to reach properly when mismatched. Your adjusting screws should be 'in the middle', not at either end of their threads. The geometry difference between the two sizes will cause the tip of the rocker arm to not push squarely against the valve stem tip. You may be able to make it 'run' with the mis-match, but it won't run well, and maybe not for long.
One manual specifies valve clearance a I=0.06mm E=0.08mm which equal 0.0024" and 0.00315" respectively, FWIW. If you are going to set at 0.004" it may be noisier. Closer clearance will give more cam duration by a smidge.
Last Edit: Oct 7, 2020 10:10:55 GMT -5 by GrumpyUnk
It's not how hard you work, it's how much you get done. simplificate & add lightness
Senna1Rossi: Thanks renagade281!
May 23, 2016 14:59:12 GMT -5
Fox: I don't really know how to say this but straight. I am Dave's Girlfriend Kellilee and bluntly and VERY SADLY he passed away early Tuesday morning. I know he would want ya all to know this. Thank You Brent for befriending my love he was very happy on here!
Jun 18, 2016 16:26:04 GMT -5
Fox: www.gofundme.com/29mgf6b8 I hope it is ok to pass on his gofundme page link. If not you will un-post it I'm sure. Thanks again all!!
Jun 18, 2016 16:31:18 GMT -5