Honda Twins banner
1 - 20 of 36 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
so this is one of a few restorations that i have going on at the moment and i was at a point were i thought it would be a good idea to start a project log to document and show guys some ideas on tackling some of this stuff including the famed rocker issues on these not going to say i have all the answers but merely how ive attempted to tackle them ive always had a huge soft spot for honda twins and its taken me a few years to find a 71 cb450 to restore i always loved the valley green metallic on these and it being a one year only color meant i had to find a 71 i didnt start with a whole lot as you can see it has a later front end a 72 on tank a 16in rear wheel and a 350 seat cobbled onto it.



this is the current state all stripped and organized ready for sandblastig polishing and painting


i decided to get the motor apart also to see what that might need i feared cam followers and an overbore at a minimum. when apart my suspicions were confirmed along with a wore out set of cams
[/url] the follower on the left was in very usable shape so i merely reground the profile the other three will need to hardfaced and reground wich led me to build this fixture to maintain the correct arc on the followers after hardface welding them up the best i can determine they seem to fall around a 58 on the rockwell scale. im not sure this is the best answer to the problem of rocker wear but i refuse to pay over a 100 bucks a piece for new ones and so far this has only cost me money for some hard tig rod and a day to build this fixture
time will tell if it will hold up. also ive got the cylinders overbored .5mm im just waiting for my honing oil to show up to final hone
as i make farther progress ill continue to update everyone on the progress

dalton
 
  • Like
Reactions: Brookesy

·
Registered
Joined
·
13,085 Posts
Interesting jig for follower cleanup. You obviously have some machining background, you and Lefty should enjoy exchanging ideas. I'd be curious to see the cams that came out of the engine, I've seen lots of followers that looked worse than those (although your pics don't zoom much as uploaded). As for $100 replacements... can't disagree with you there. MegaCycle gets $100 to weld and hardface (don't know what their hardface registers on the Rockwell scale) but Delta does follower repair for under $20 each and their work looks good. Oiling is the key to longevity on 450 cams and followers, so be sure your oil pump and passages are good and assembled properly
 

·
Registered
Joined
·
308 Posts
Perhaps you could have them hard-chrommed. I've done it a few times when I was restoring some similar mechanical stuff. The chrome is quite hard (I think around 70 HRC), and I've heard it's often used for such applications. It's also quite cheap (atleast where I had it done).
 

·
Registered
Joined
·
523 Posts
nice! color me subscribed to this thread.
J
 

·
Registered
Joined
·
2,837 Posts
Good stuff. I made a follower grinding jig that consisted of a table with a slot where a grinding wheel protruded. A diamond point would true it flush and the follower bolted into a jig with curved side rails, kinda like a mini rocking horse. Then you'd grind it down by hand. I've never tried it. I've read an article saying how someone experimented with different weld materials but I'm pretty clueless about that. Looking forward to more posts.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #7 ·
heres a couple shots of the cams that came out of it i think there still functional as the engine seemed to run ok before tear down. i just felt if i was going this far i might as well change anything questionable. also i was able to secure an nos set of cams off eBay.

as far as hard chroming the rockers i had toyed with the idea but at 70rc i worried about that being to hard to run against the cams and damaging the lobes. it does appear if they were plated with something originally exactly what i have no idea.


Lefty sounds like you've certainly put some time and effort into fixturing to properly regrind these followers as well. i merely adapted what i had on hand to get the best result i could i dont believe they need to be super accurate being they wear in severely and still work just fine. as far as welding them up i hunted around until i found a tig rod that was in the hardness range i feel most closely matches the base metal which actually turns out to be a tool steel welding rod. whether it works or not well find out i think with all the collective ideas and thought processes ive seen on here i think a viable solution to the follower wear can be achieved thats not proprietary to the few company's offering the service
 

·
Registered
Joined
·
308 Posts
as far as hard chroming the rockers i had toyed with the idea but at 70rc i worried about that being to hard to run against the cams and damaging the lobes. it does appear if they were plated with something originally exactly what i have no idea.
Well, it is definitely easier to re-weld and reshape the rockers again, if you will have wear problems. Reshaping the cams would be more problematic...
 

·
Registered
Joined
·
13,085 Posts
From the look of the cams and followers, I'd say it's possible that amount of wear was simply caused by poor warm-up habits over the years by impatient owners. It takes about 1 to 2 full minutes for oil flow to reach the top end of a DOHC 450 and those who want to ride almost immediately after starting put those parts under more load than they can stand without oil flow, causing a bit of wear each time due to high friction levels before steady oil flow reaches the cams. Since the engine design leaves the cams out in the open with no accumulated oil lying underneath them to "dip" into each rotation, the parts rely on oil flow only.
 

·
Registered
Joined
·
308 Posts
From the look of the cams and followers, I'd say it's possible that amount of wear was simply caused by poor warm-up habits over the years by impatient owners. It takes about 1 to 2 full minutes for oil flow to reach the top end of a DOHC 450 and those who want to ride almost immediately after starting put those parts under more load than they can stand without oil flow, causing a bit of wear each time due to high friction levels before steady oil flow reaches the cams. Since the engine design leaves the cams out in the open with no accumulated oil lying underneath them to "dip" into each rotation, the parts rely on oil flow only.
The oil used has probably a lot to do with it too. Older oils had a lot of phosphorus in them, which was actually better for less wear on the followers. Airhead BMW and Moto Guzzi owners have experienced a lot of wear on the tappets with modern oil, and I think it is suggested to use SF rated oils only. I think this is less of a problem on Hondas, since they have a more modern design... Also, some moly additive in the oil may help a lot (leaves a coating over the parts, so when the engine starts, they are still slightly lubricated, until the oil comes).
 

·
Registered
Joined
·
13,085 Posts
The oil used has probably a lot to do with it too. Older oils had a lot of phosphorus in them, which was actually better for less wear on the followers. Airhead BMW and Moto Guzzi owners have experienced a lot of wear on the tappets with modern oil, and I think it is suggested to use SF rated oils only. I think this is less of a problem on Hondas, since they have a more modern design... Also, some moly additive in the oil may help a lot (leaves a coating over the parts, so when the engine starts, they are still slightly lubricated, until the oil comes).
Agreed - I've gone to Brad Penn oil and use a ZDDP additive as well, but my 450 is a part-time use bike that only goes out on nice, dry days...
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #12 ·
Well, it is definitely easier to re-weld and reshape the rockers again, if you will have wear problems. Reshaping the cams would be more problematic...
my thoughts exactly id rather sneak up on the ideal hardness rather than overshoot an ruin a set of cams
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #13 ·
Agreed - I've gone to Brad Penn oil and use a ZDDP additive as well, but my 450 is a part-time use bike that only goes out on nice, dry days...
i also use brad penn v2 oil in all my bikes for years and have had great luck with being its designed for wet clutch air cooled bikes
 

·
Registered
Joined
·
13,085 Posts
i also use brad penn v2 oil in all my bikes for years and have had great luck with being its designed for wet clutch air cooled bikes
Yeah, having been out of the Honda twins game for a long time before starting my project back in November 2016, I wasn't aware of the changes in oil that affect flat tappet engines until last year. All is well now
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #15 ·
well today my welding rod for the followers showed up so i was able to try that out i chose i chose an a7362 alloy rod to try first as it falls from a 54 to 60rc hardness i also got some hs7 alloy rod wich is just a touch softer as i couldnt make up my mind on the one i wanted to use . i opted for the slightly harder a7362 and was very happy with how it layed out

i also was happy with how it came out after grinding the big test will be how they hold up in the engine after some miles


the one interesting thing i noticed after i got done and was cleaning up the follower is it almost appears like these rockers are cast and then a hardface pad is actually fused to it heres a picture of what sparked that thought
 

·
Registered
Joined
·
2,837 Posts
The Honda service manual says they have a stellite welded facing. Not sure how thick but it looks like your entire pad is cracking off. Did you grind em down good first, preheat, and let cool slowly? Maybe bury in kitty litter?
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #17 ·
interesting and i did preheat and cover in insulation afterwards but it might have cooled to fast maybe ill put them in the oven afterwards and slow the cooling even more. good to know there stellite i wasn't aware of this. i actually was debating about using a stellite rod originally might have to get some of that to try.
 

·
Registered
Joined
·
3,537 Posts
Nice work on the grinding. I like the fixture. Stellite is an old proprietary trade name for a hard surface weld. It has been around since WW1 and it revolutionized poppet valves for IC engines. I'm sure there are other steel alloys around that will work as well or even better. RC 54-60 should be fine for the follower face. It is very difficult to get steel any harder then Rockwell RC 60.
When reshaping the cam follower face, the dimension from the center of the eccentric pivot bore to the tangent point of the follower face where it contacts the cam is critical. Any error in the tangent point will cause errors in the cam timing.
 

·
Registered
Joined
·
2,837 Posts
Nice work on the grinding. I like the fixture. Stellite is an old proprietary trade name for a hard surface weld. It has been around since WW1 and it revolutionized poppet valves for IC engines. I'm sure there are other steel alloys around that will work as well or even better. RC 54-60 should be fine for the follower face. It is very difficult to get steel any harder then Rockwell RC 60.
When reshaping the cam follower face, the dimension from the center of the eccentric pivot bore to the tangent point of the follower face where it contacts the cam is critical. Any error in the tangent point will cause errors in the cam timing.
Or you could grind a little extra off to make up for a valve seat cut a little too deep. I had six followers ground from delta at $8.25 a pop. Quick measurements point to them just grinding, not welding.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #20 ·
Nice work on the grinding. I like the fixture. Stellite is an old proprietary trade name for a hard surface weld. It has been around since WW1 and it revolutionized poppet valves for IC engines. I'm sure there are other steel alloys around that will work as well or even better. RC 54-60 should be fine for the follower face. It is very difficult to get steel any harder then Rockwell RC 60.
When reshaping the cam follower face, the dimension from the center of the eccentric pivot bore to the tangent point of the follower face where it contacts the cam is critical. Any error in the tangent point will cause errors in the cam timing.
thanks it took me quite a lot of time measuring and figuring to get it right i have 2 pages of drawings and math to prove it lol. Thats also good to know on the stellite that by using a similar but different rod im not barking up the wrong tree.


Or you could grind a little extra off to make up for a valve seat cut a little too deep. I had six followers ground from delta at $8.25 a pop. Quick measurements point to them just grinding, not welding.
i wondered if that was what alot of these places were doing just grinding them down until they were cleaned up but at what point do you run out of adjustment on your valve lash.

i was able to get the other two rockers that needed welding built up and reground without any cracking at the edge of the pad i went with a more extensive preheat and lengthened post heat as Lefty suggested might be my issue.
 
1 - 20 of 36 Posts
Top