Valve guides again

Purchased Kibblewhite bronze guides and new valves from Brit cycle. Installed guides easily (bake head at 500F, drop in chilled guides, 2 taps to seat). Cast Iron guides said to be no longer available.

Go to lap the valve seats and they don't fit! 0.311 dia. valve stems. Can't get venier caliber into guides but looks to be 0.31 +/- as well.

I would have thought they should have fitted without machining. Now I have to source a reliable shop in Toronto.

Kinda PO'd.

Spec's indicate 0.001 clearance for IN and 0.0015 EX. Could (should) I achieve this with a light hone inside guides?

Thoughts comments appreciated. Not interested in pressing out the bronze guides.

The guides close up as they are installed and a good valve fit prior to installation will result in the valve not fitting after. You need to hone the Kibblewhite guides and the Kibblewhite bronze material blunts HHS reamers within a few turns so you need a Flex hone of 8mm/5/16" instead.

http://www.brushresearch.com/flex-hone.php

I used 2 adjustable reamers to sneak up on it, a 9/32 to 5/16 and a 5/16 to 11/32. I am sure there are machine tool supply houses around Toronto who will have these.

Thanks Pete. That's what I'll do.

Any shop that does cylinder head rebuilding has a valve guide hone that would size the guides to the desired fit in short order.

I've installed quite a few KPM bronze guides in Commando heads, and they always require reaming or honing after installation. I think that's pretty standard procedure for bronze guides in high performance applications, where you want to keep the clearance tighter than for cast iron guides. I've used both reamers and hones, but for reaming bronze, you really needs carbide reamers, and they are something like $270 each (US$ price). A Sunnen hone is even more expensive, but at least is useful for a variety of valve stem sizes. You can also buy a flex hone for 5/16" guides for $20 or so, and that might be your simplest option, but you have to be careful with it not to bell mouth the guides. I buy most of my valve work tools from Goodson at www.goodson.com.

It is possible to ream bronze guides with HSS reamers, but you really have to be careful about speed and lubrication. It's pretty easy to dull the reamer. Bronze guides also seem to come out a little undersized from the stated reamer size. Using a .311" reamer on bronze seems to result in a finished bore of .3105, or even .310".

Like WZ507 said, your simplest solution is probably to just take it to a reputable cylinder head shop.

Ken

pete.v said:

I used 2 adjustable reamers to sneak up on it, a 9/32 to 5/16 and a 5/16 to 11/32. I am sure there are machine tool supply houses around Toronto who will have these.

Click to expand...

I don't think that 4 blade reemer is very good for Bronx or brass. Tends to chatter. spiral reemer is better, but take the advice of other who have suggested taking head to a good engine machine shop,.
'Dereck

Stillreel said:

Cast Iron guides said to be no longer available.

Click to expand...

Highly unlikely.

Cast iron guides still available from Andover, RGM, etc.

Ken

pete.v said:

I used 2 adjustable reamers to sneak up on it, a 9/32 to 5/16 and a 5/16 to 11/32. I am sure there are machine tool supply houses around Toronto who will have these.

Click to expand...

This worked really well. Such an easy job really. I don't know why so many others insist on going to a machine shop.

Ha. Just recently been there, done that. Bought the Kibblewhite guides from Old Britts, new valves and bee-hive springs from JS Motorsports. Baked the head to the Workshop Manual and Haynes recommended 200° (500°! Holy shit), pounded in the frozen guides and went to slide in the valves. No workie. Miked Jim's valves and they were the precise max diameter prescribed by the Manual — to the nearest ten-thousandth. Since my 8mm drift was a near interference fit in the Kibblewhite guides, I miked it and the measurement was off, as near as I could tell, by .0005". Given the maladroit I can occasionally be, this falls well within the range of personal measurement error, meaning the valves and guides were a non-negotiable interference fit. I wrote a nasty-gram to Ella at Old Britts blaming Kibblewhite. She allowed as how their needing reaming was a given and probably should notify purchasers of this presumed known fact. Fortunately, Brian Billings at BBRP here in Bellingham had the proper ream in stock, and problem easily solved. I purchased my first British motorcycle, a 1956 Matchless G11CSR in 1962 and I'm still learning new quirks about working on these damn things.

The new valves drop in to the new guides under their own weight for an easy sliding fit. I'll put the head back on once it warms up a bit here. -20C outside today (*erk!)