Valve shims

[Kab wilcox]

I have a 1980 CB750F have spark and fuel plus it has the top end rebuilt. But it seems that it pushes air back through the carb before the intake stroke. Everything is pointing towards the valve shims. Just wondering if it is easy to change the shims while the engine is still in the frame? Because I really really don’t want to take the engine off the frame. Lol any feedback would be appreciated thx.

 

[jpdevol]

Can do....just remove the valve cover and follow the manual's procedure. Of course, you'll need the tool to hold the bucket depressed if you need to change shims

 

[Kab wilcox]

How long would it be with the tool approximately

 

[jpdevol]

When working on old bikes, one never knows with any job.....I suspect an hour if everything goes right and no shims need replaced - add a half hour for the first shim and 15min for each successive one and factor in things that are stuck that shouldn't be, things that need cleaned: call it 4 hrs

 

[Kab wilcox]

Well I suspect that the job will take 4 hours then waiting for the parts to arrive lol for got to keep the camshafts with the head when the valves got regrounded so they could replace the shims (head slap) lol

 

[Brad C]

I have a 1980 CB750F have spark and fuel plus it has the top end rebuilt. But it seems that it pushes air back through the carb before the intake stroke. Everything is pointing towards the valve shims. Just wondering if it is easy to change the shims while the engine is still in the frame? Because I really really don’t want to take the engine off the frame. Lol any feedback would be appreciated thx.

Did you check your valve timing? It sounds like it may be 180 degrees out.

 

[Kab wilcox]

Nope timing is good but I have blow back through the carb so the valves are not sealing, so after thinking about the rebuild . I did not check the shim clearance. So I am waiting for the tool to get here and I will check all 16 shims. Probably will have to get some different shims. Still looking for a kit for a fair price.

 

[mrtwowheel]

Any good Honda shop will have a large box of shims in the back. That guy at the parts counter doesn't have a clue. These shims are not in the inventory. Used shims are just fine, they never show any wear. Take your calipers or mic, tell the guy at the counter that you want to see the box of shims that the techs are hiding out in back. It may take a while to find them but just keep insisting that they are there. After swapping my shims around and a lot of MATH, I normally only need 2 sizes that I don't have on the bike.

Scott

 

[Kab wilcox]

Any good Honda shop will have a large box of shims in the back. That guy at the parts counter doesn't have a clue. These shims are not in the inventory. Used shims are just fine, they never show any wear. Take your calipers or mic, tell the guy at the counter that you want to see the box of shims that the techs are hiding out in back. It may take a while to find them but just keep insisting that they are there. After swapping my shims around and a lot of MATH, I normally only need 2 sizes that I don't have on the bike.

Scott

Ok thanks for the info