Sorry. My brain was thinking pushrod when you said connecting rod. You do have connecting rods.
Lol no problem does it sound like it could be the con rods?irk miller said:Sorry. My brain was thinking pushrod when you said connecting rod. You do have connecting rods.
Contact Lani at Copper Gaskets Unlimited... http://www.coppergaskets.us/ . He can make them in a plethora of thicknesses. Give him a call and talk through it. I put his gaskets on all of my machines, especially the ones I have bored out.quadracer351 said:Ticking problem solved! Wrong gasket was put on, .040'm was on when we're thinking I need a .060~.070I'm because of the profile of the Pistons. Pistons 4 and 2 were making contact with the sides of the dome and the sleeves around the exhaust valves. I have some plastiguage in the mail and need to see if anyone on this forum is making custom thickness gaskets if not I'll just get one online
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Love it, thank you!irk miller said:Contact Lani at Copper Gaskets Unlimited... http://www.coppergaskets.us/ . He can make them in a plethora of thicknesses. Give him a call and talk through it. I put his gaskets on all of my machines, especially the ones I have bored out.
Love it, thank you!irk miller said:Contact Lani at Copper Gaskets Unlimited... http://www.coppergaskets.us/ . He can make them in a plethora of thicknesses. Give him a call and talk through it. I put his gaskets on all of my machines, especially the ones I have bored out.
DOHC rods interchange, but they're 1mm shorter. CB900 and CB1100 rods interchange, but they're 1.5mm longer. All three cranks interchange as well, but with different strokes. I don't know what work was done to the motor, but there are interchanges that effect those numbers. Is it possible that the wrong combo of rods and pistons is at play here?teazer said:Conrods rarely have that much difference and pistons made in the last decade or more should close to identical.
They are no longer made found them online a few years ago when looking for Pistons. They were manufactured in the late 70s early 80s I believe. Up until last year I was still finding them randomly for sale online. I'll see if I can find anything else about themteazer said:Those are odd looking pistons. A SOHC 750 has inlets and exhaust valves offset and as a result the valve pockets are offset from the center line. The crown on most 811 kit pistons is more of a gentle curve. Maybe because teh original 64mm pistons were machined out of CB350 OEM stocks.
The crown shape and valve cutouts look wrong, but I don't claim to recognize ever piston ever made. Those look like they were manufactured a while ago. The head profile doesn't look as if it matches a SOHC head, so it's a bit of a puzzle as to what they were supposed to fit. TRW don't seem to list anything in their current (Federal-Mogul) catalog for a SOHC.
The crowns look tall compared to an average big bore SOHC piston so maybe they were a very high comp race piston or something.
What do we know about those pistons?
irk miller said:Your CB750 doesn't have connecting rods.
crazypj said:What connects the pistons to crank?
This motor has been out 3 times this month. I measured all the cylinders at tdc across the head and I got the same measurement for all. I honestly think it's the way the domes are situated in 2 and 4 that is causing a little interference. I had the plastguage come today but won't be trying it till later this week. Hopefully that will give me a better idea of the clearances through out the piston head. As far as the gasket goes it seems the consensus is the base gasket will be the better of the two to go a little thicker on. Guess I'll be needing two in the end since the head one is also custom for the larger piston diameter.crazypj said:What connects the pistons to crank?
The piston height should have been checked before the head was fitted, one of the guys doing a CB378cc conversion is having similar problem due to production variations. I've done a few 378 motors and didn't need to get 'special' gaskets but obviosly there are dimensional differences between various year motors.
You either machine piston tops or fit thicker base gasket to get a total clearance of 0.038"~0.040" piston to head clearance. CB750 motor weighs 210lbs and IS a PITA to get in and out of frame all the time (no way could I lift one out on my own like I used to at 21 )