'78 cb750F3 Exhaust guides

[garyS-NJ]

Yes mine are a little tired so I'm looking at the cycle-X extra long (49.5mm) cast guides or bronze guides from APE or Dynoman. I'm hearing the Cycle-X guides mfr'd by Kibblewhite were designed to address the F2/3 design issue but others are saying go bronze/. I'm thinking the cast might be more durable if I ride like a granny but the bronze will be more durable if I do a lot of riding around 7k R's (with the occasional high speed runs and top end blasts). And if bronze is batter (manly recommends cast for street and bronze for racing), why didn't cycle-X get their long guides made from bronze? any suggestions on which way to go and sources?? Oh, and what about ampco45 vs C63000 guides (Dynoman offers both).

and then I might need some valves or take the plunge for a full set aftermarket (I'm already buying the titanium retainers.). APE has the iconel Stainless and Dynoman has the nitrided stainless. haven't found anyone with a hard chrome stems. Any suggestions on valves and is there any issue of matching valve stem material to valve guide material?? Manley for Harley says their Nitrided Valves are compatible with their cast or bronze guides but TRW site talks about different stem coatings for different guide material. What is the common knowledge for the F2/3 head and for valves to work in those guides..??
garyS

 

[dirtdigger]

Unless you are set up to cut your own valve seats you will need to send off your head for a valve job after replacing the guides because the valve stem will no longer be concentric with the valve seat. Replacing the guides can be difficult and you can damage the head if you are not careful when removing the old guides. I have done both and its not fun if you haven't done this work before. I would send the head to APE as they have a specific F2 head rebuild program and have built these engines from the day Honda released them. I would go with APE guides and valves as there parts are used by many other head shops. Cycle X guides are very new to the market and I have not seen or heard of any durability reports yet, but bronze guides have been used forever and are proven to work. I have used Cycle X valves and APE valves but I would say the APE valves are the best on the market. If you have never done head work or if you dont have a shop nearby that has any experience with the 750 motor I would send it to APE, they will fix you up and know it is done right...they have the experience to back it up.

 

[garyS-NJ]

I'm sure APE would do a fine job but they aint cheap. And cycle-X cast guides I have to imagine are at least as good as oem guides because they are being made by kibblewhite. I'm wondering why just the exhaust guides go on the F3's and would like to address that issue. most folks say it is the higher spring pressure and shorter valves (change rocker to valve geometry) and to address this, I don't see bronze guides fixing anything. Yes, they might provide better lubrication at high rpms when oil might be starved and perhaps that is when the F3 oem cast guides are wearing out but I didn't see any evidence of oil starved on the valve stems (no blueing or gauling). I'm thinking the guides are just wearing from lateral loads and I understand that a cast guide would be harder to wear or deform than a bronze guide and then also Ken's longer cast guide might provide more support (and spread out the lateral loads).

I reached out to TRW Valves and manley valves for their recommendations on guides and then valve/guide combinations. Only TRW responded and only about the combinations. They said cast iron guides need nitride stems or chrome stems but "plain steel" valve stems need bronze guides. This has me wondering tho because my stock OEM valves I think are some sort of stainless steel and I don't think the stems are chromed (and of course the stock OEM guides are cast iron). Anyone know what the F3 OEM valves are made of or finished with??

 

[dirtdigger]

Actually the stock guides are a very poor material and is a contributing factor in the wear. No matter which guide you use you will need a good valve job after replacing the guides. If you are worried about compatibitly between guides and valves then just buy all of your parts from one place. Buy a Cycle X kit or parts from APE. I use stock and aftermarket valves in APE bronze guides never have issues. The cast guides may or may not fix the problem...its too early to know as they are new to the market. The bronze guides have never caused any issues. The bronze guides are far superior to the stock honda guides and will outlast stock guides. And yes the guide wear is a result of laterial wear which you can never get rid of with a rocker arm motor which gets worse with higher lift cams.

 

[garyS-NJ]

Thanks Dirt Digger, this picture is becoming a lot clearer for me. Last point tho. after 35k miles, only my exhaust guides were worn and the valves only had slight dishing on the tops. My intake guides felt nice so I was thinking only replace exhaust guides and re-use all the valves with just a clean up gring to make the tips flat and smooth (I read that the tops if coated with stellite will be 0.040 to 0.080 thickness so taking 0.020" off is OK). So I'm thinking only replace Exhaust guides with Dynoman's AMPco45 or C6300.. But on my valves, when I finished cleaning the carbon off the faces and backs I am left with some areas polished silvery and other areas polished shiny black. I was worried I might have wirewheeled or scraped off some finish (but if it was stellite it should have been too hard and also at least 0.040 thick?).. Do you know anything about the materials and finish on these stock valves (yes, bronze guides will go with the stems but did I degrade the faces/backs?)./