Oil Pump Binding

I'm reassembling a CT70HKO. Using a Vesrah gasket set. When I took it apart, I noticed the oil pump bolts were loose. Should they be screws instead of bolts or does it matter?

Putting it back together and the oil pump spins free and easy up until I put the final torque on the bolts.
The manual I have says 6-9 ft. lb. on the bolts. I used 84 in. lb. to torque them but it binds. If I hand tighten them with a nut driver, it'll spin fairly easy but I can tell there's a little bit of bind.

The pump itself is in good shape as far as tolerance with a feeler gauge. There is sufficient end play in the shaft.

The gaskets in the kit are paper thin and I think too thin.
Has anyone ran across aftermarket gaskets being too thin, causing the pump to bind when it's tightened down?

Those gaskets are supposed to be paper thin and those bolts were originally JIS screws. I've never run across too thin of a gasket with aftermarket. I'm thinking the pump plate might be warped/bent. When tightening, I just bump them with a handheld impact.

I've never tried it, but maybe doubling the gasket would do the trick. I dont think these pumps generate alot of pressure. I think its only 3-5psi. I would however, like to see a pressure gauge on one of these engines, just to see for sure.

Oh yeah, I've run into this...still do, from time to time. You're correct, gasket thickness does vary and, in some cases...like this one...it makes the difference between turning freely and binding. Props to you, for thoroughness. This isn't super common and I doubt that many guys would even think to check for oil pump bind. IMHO, best bet would be to just source an OEM gasket. Running two gaskets, if strictly needed to avoid binding, should be okay; the thinnest gaskets are ~.002"+/- thick...IOW we're not talking about significant stack height changes.

And Chett is 100% correct, the oil pump should be mounted using JIS screws, not hex bolts. Those are still available as new, OEM, parts.

Thanks for bringing this topic up . I will definitely be checking that when I begin to re assemble my engine. I have one of the Trailbuddy gasket kits.

Got an OEM gasket and screws ordered.
Thanks.

Kurt

Got the Honda gasket and it measures .005" thick. The one in the Vesrah kit measured .003".
That extra .002" made all the difference.
Just another example why it's smart to go OEM parts if you can.

Kurt

wanrep said:

Just another example why it's smart to go OEM parts if you can.

Kurt

Click to expand...

Thats why I always do. A few times I didn't and ended up replacing with OEM later. Even used OEM is better than alot of aftermarket. One example was the time I had to change the swingarm bolt in my brothers K3, because the threads were messed up. I replaced it with a brand new aftermarket that I had. It snapped after a few rides. Did some hard searching and found one out of a 1980 CT70 that I forgot I had. It was a bit rusty, but over a 1000miles later, still works fine.lol

Funny (as in "peculiar", not "ha-ha") thing is that the thinner gasket will work, no problems, in most engines. Best guess, it comes down to oil pump variations. And gasket thickness varies in aftermarket kits, too. For the DIYer, there's no better failsafe than OEM, for sure.

As for critical fasteners, most are all but limited to OEM. The axles and upper motor mount are proprietary bolt designs...IOW ain't gonna be found in a hardware store bin. IMHO, the swingarm pivot bolt is the most critical fastener on the entire bike; failure could result in dumping the bike. I've only had an upper motor mount fail, once, never a swingarm pivot bolt. Used OEM fasteners can fatigue, rust and eventually fail, under the right circumstances; they should be inspected, not taken for granted. . If you're going to source aftermarket bolts, you'd best know your way around fasteners...not exactly water cooler discussion material. If in doubt, order new OEM...it's cheap insurance, easier, too.