850 R10 Head Valve guides--Brass or Steel

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Mar 1, 2007
The valve guides in my 1974 850-- R10 Cylinder head are made of brass. Do you think these were stock or should they have been cast iron or steel??? The head only has 2000 original miles but the previous owner pulled the head and polished the intake ports and rocker arms likely at Storm Cycles in Texas years ago. There were also roller washers installed inbetween the rockers and the edges of the inside of the heads. Why polish the rockers and why the roller washers???Valve stem wise there is not much axis to axis side play so I am thinking I will just lap the valves with a good compuond and go ahead with re-assembly. The valve edges and seats look great with no pits or burns. I will be an occasional weekend rider. No trips longer than 150 miles rarley. Thanks for any advise--Mark C.
I believe the stock valve guides were cast iron, but many replacements are phosphor-bronze.

Since the ports were polished, I would suspect they removed the valve guides during this process. Rather than try to replace the original guides (not recommended) they installed the bronze replacements.

I'm not sure I know what you mean by "roller" washers, but it is a typical hot rod procedure to replace the springs on the rocker spindles with solid washers to positively locate the rocker. Polishing the rockers usually involves removing a significant amount of metal and therefore lightening the valve train. This is usually accompanied by alloy or titanium (preferrable) spring caps, drilled cam tappets, and stronger valve springs.

This is getting into some serious engine mods for an 850. Has the head been milled? A give away is flycut pistons like a 750. Are the intakes stock size or oversize? Have the intake ports been enlarged from 30mm to 32 mm?

If the ports and rockers have been modified I would suspect the camshaft is no longer stock either.
850 head valve guides

Thanks Ron. What do you mean by drilled cam tappetts and flycut pistons?? The pistons were perfectly flat on top -no dome and no relief cuts to clear the valves?? The tappetts in the bottom of the cylinder had no holes drilled that I could see. It did not appear that the engine cases had been split although I should have checked the cam lift. The mains were perfect after serious inspection with a magnifying glass. so when I split the cases I replaced only the rod bearings and seals. The rod journals were perfect with no damage and the rods were stock The roller washers did replace the spring washers in the valve train. I have the head on the way to Fair spares to get one exhaust thread repaired so I will check the polished port size when it arrives back next week. What impending problems for a weekend rider if it has a high lift cam and heavier springs??? This all should help with higher revs. Do you know how to test the springs to see if they are stiffer than stock. I assume this would lead to faster cam lobe wear??? Thanks for any help--Mark C.
I didn't mean to get you all concerned. It's just that if someone went to the trouble and expense to polish the ports and lighten the rockers, they usually would have done the easier mods as well.

If the head had been milled to raise the compression, or a high lift cam installed, the pistons would have needed valve reliefs (flycut). Since this is not the case with your engine, it is safe to assume you do not have a milled head or high lift cam.

If you have access to a new stock valve spring, you could compare free length of one of your installed springs. Stiffer springs usually have a longer free length than stock. Again this would be an unusual mod with a stock cam.
Thanks Ron

I really appreciate the advise Ron. I will check the spring length with the manuals I have or another heads stock springs that I have. I really just want a pretty stock engine. I agree that it is odd that the work was done on the valvetrain but not the cam or head & pistons???. Seems like litttle gain for a hot rodder. He also had a 19 inch counterssproket on it that I have replaced with a 21 tooth. High compression and a higher rev engine would just spell headache for a 53 year old like me. I just want a good looking reliable ride. A commando thats been setting in grandpas pasture and rusted for years still looks better than most Harleys----And we get the chicks-----
That is actually how my cafe racer came to be. I bought a rolling basket case to get the Dunstall double disc front end. As I dug deeper, the box of transmission parts had an extra gearset. Turned out it was a Quaife 5-speed. (I had fun trying to put that back together with no diagram!).

When I lifted the head off the engine I found oversize re-angled valves, an obvious port job, lightened rockers, and valve reliefs in the 850 pistons. The head had been milled until the first cooling fin was about half the size of the rest! The cam was an obvious re-grind, but I have never taken the time to try to figure out the lift and duration. (It was replaced with a 4S grind.)

All this in a frame with a king and queen seat, 16-inch hog wheel and ape hangers!
Mark Cigainero said:
Why polish the rockers and why the roller washers???

As Ron L has said, the bronze spacers are a common 'performance' modification fitted in place of the spring washers, and I have them fitted to my own 850 big valve head, which also has polished rockers.
Phosphor bronze valve guides are a popular replacement choice because their thermal expansion is similar to aluminium. This means they are less likely to come loose in the head as it heats up.

Rockers are lightened and polished to reduce mass in the valve train and to make them less likely to break by removing any areas that may initiate a crack. ( Commando rockers are not known for being weak as far as I know).

The washers reduce friction that is caused by the springs on the rocker shafts.
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