Combat Camshaft Bushes

I realize that this has been discussed a few times, but I can find no consensus and I've done a little investigation and have decided what to do - I hope it helps others.

I'm rebuilding two Combat engines right now. Both had a bush that looked like 06.2600 except that one had no grooves inside. Both are clearly from the factory - both have a split in the side and oil hole is not round.

The engine with no grooves has a 2S camshaft with no scrolling. The other engine had a bad aftermarket camshaft. Both engines had the tab thrust washer 06.2601 on both side of the case and all four had cracks in the tabs.

I happened to have a 06-3020 bush in stock so I wanted to know how that would work so I assembled the cam, beveled washer, 06.3020 and sprocket outside the case and verified that I had end play (0.015"). That left me with one problem - that cam wasn't scrolled. So, I checked the new cam I bought for the other engine and it is scrolled.

I've replaced the 06.2600 with the 06.3020, installed the new cam, and that engine is now good. I'll get a price on getting the other cam scrolled and decide whether to do that or to install a new cam in the other engine.

The workshop manual warns not to replace cam bushings, but with some heat and cold, it was not particularity hard, and now I don't have to worry about having tab thrust washers. I didn't like the thought of using them without the tabs and I really didn't like the thought of using them with the tabs!

Bushs - picture from the Old Britts web site.

I have a 2S cam which I wanted to fit into an 850. It has no scrolling so, I tried to cut it by hand. The result is OK but ugly. Ashleigh has fitted a 2S cam into an 850, so he would probably know which cam bushes are appropriate for both the 750 and the 850..

PM sent - check your inbox

Comnoz can do the scrolling on the cam I think. I have a spare non-scrolled 2S cam that needs doing also. I think there was a good thread recently where dynodave explains all the ins and outs of cam bushings.

https://www.accessnorton.com/NortonCommando/camshaft-conundrum.29739/
time warp pix very helpful...

dynodave said:

https://www.accessnorton.com/NortonCommando/camshaft-conundrum.29739/
time warp pix very helpful...

Click to expand...

Studied that thread yesterday but never found consensus on my issue. Since my bushing was one that supposedly never existed (06.2600 with no groves), and since I'm not comfortable with keeping the tabbed thrust washers without (or with) the tabs, I decided to change the bushing and camshaft.

When I started looking, I expected to see people explaining why it is OK to remove the tabs and (possibly) let the thrust washers turn against the crankcase - never found that.

batrider said:

Comnoz can do the scrolling on the cam I think. I have a spare non-scrolled 2S cam that needs doing also. I think there was a good thread recently where dynodave explains all the ins and outs of cam bushings.

Click to expand...

Yes he did mine.

marshg246 said:

Studied that thread yesterday but never found consensus on my issue. Since my bushing was one that supposedly never existed (06.2600 with no groves), and since I'm not comfortable with keeping the tabbed thrust washers without (or with) the tabs, I decided to change the bushing and camshaft.

When I started looking, I expected to see people explaining why it is OK to remove the tabs and (possibly) let the thrust washers turn against the crankcase - never found that.

Click to expand...

once the tabs are broken off, the washer can spin on the aluminum. In this case (ALL NHT ) cases are not meant to be a wear surface. I consider it an extremely inferior engineering choice. But I have seen folks offer it....but not me!
No one offered it ...maybe people are waking up.