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Mix n Match Cams

  • Thread starter Thread starter Buster-boy
  • Start date Start date
B

Buster-boy

Guest
Can I use cams and caps from one head on another or are they machined specifically for that partcular head? The spark plug threads on mine are a little stripped - not too bad but enough to give me headaches. I have an opportunity to buy another head but all it has on it are the intake boots and valves, whereas mine is complete. I should be able to use my cams, caps/bearings, and chain tensioner on the other one, right?
 
You STILL don't have that thing running? ;) actually it generally isn't a good idea to mix and match cams and you pretty much hit the nail on the head with why. The cam journals and bearings/caps wear as a unit. It could cause premature failure to mix them (which is why if you noticed they are lettered to match the corosponding letter down in the head so you don't mix them up within the head). If you have a bad plug hole or two (heh he said plug hole) I'd suggest removing the head and having them helicoiled or time serted at a shop (with plug holes or bolt holes where you are routinely removing the plug or bolt I prefer timeserts as IMO they are much more stable and much less likely to back out of the hole with whatever you are removing from it, however done RIGHT helicoils are just as acceptable. Esspecially in steel. I don't care for them in aluminum but that's just me.)

Having said that and this may raise the ire of some of the members perhaps, if you have no intentions of removing the head ( do NOT helicoil with the head on the bike. Shavings will end up in your crank and that's bad news) then *I* have used second hand cams a couple of times. However I would suggest you use the caps that were in the head to begin with if at all possible. Some may disagree but it's my feeling that introducing fewer differently warn parts the better. Although in a street bike I'm not really sure it's all that big of a deal.
 
HA! You remembered! Nah, it's finally running but man I chased my tail with this thing. It needed every dime I put into it (boots, O-rings, head gasket, valve cover gasket, etc) but what really swayed me was the freakin carbs. I couldn't keep that thing running for nuthin!! Turns out they needed sync'd. Man what a difference!

But, like I said two of the plug holes (ha ha, what you said) are a little stripped way down at the bottom. They hold and I can ride like there's no tomorrow, but there's just that little bit of spittin n sputterin at a steady throttle. Accelerating I'm good, it's just at cruising speeds it acts up - kinda like when the engine is cold and you're trying to hammer on the throttle. Now I know why one of the previous owners had silicone around the plug threads.

What's kinda weird though I can be riding, or shall I say puttering along, and hit a bump and the sputtering goes away. Sometimes when I shut it down for a bit (gas station, store, etc) and start back up it goes away too. So, I'm a little puzzled why it does that. Could also be a little bit of crud in the carbs too I s'pose.

Anyway, the cams. The head is on eBay. I emailed they guy and he said I could try my cams and it may or may not work. Like you he's done it and got lucky but didn't reccommend it. I guess I'll let that one go. I thought about a helicoil but I figured that's a little pricey - more than I care to spend.

Let me ask you this - what's that whinning, whistling sound I hear coming from the front? I want to say it's an engine noise as it changes in pitch with engine speed, but I'm guessing maybe the tach or cables? Or is it the clutch? I've heard other bikes make that same noise as well, not just mine. Doesn't do it when stopped or in neutral.

Good chattin with ya, man!!

Jim
 
What year is your 850 again? I have a couple nice 750 heads which were the same head as the 79 850. In 80 they changed of course for the CV carburetors. If yours is a 79 I might be able to help you out. Or if you plan on removing the head you could contact John Pearson fromPearson Racing. He's near west Alexandria I think not too far from either of us. I sent Dogma to him for some similar issues with his 850 and he did it right there for around 80 bucks maybe? He's not expensive and the guy KNOWS these bikes. He's one of three guys in the US that the drag guys really trust to do their racing cranks. His shop is in his garage and he does it all cranks clutch baskets headwork bore kits. Builds some mean machines. Really good honest guy. Dogma had asked him if he thought he should deck the head before putting it back on and John said he'd just be taking his money. Honesty like that goes a long way toward me cracking my wallet open. At anyrate it might be worth giving him a call ( I don't have his number off the top of my head but I think he is listed if not I'll hunt it up for you)

As far as the whining noise without hearing it it could be a number of things. Could be a dry tach cable (lube that puppy with some silicone spray or some three in one or something.) could be a dry speedo cable could be the tach or speedo gears in the guages making noise could be your airbox leaking and sucking air a bit. See what I mean? Lol. Also those 8valve motors are simply a bit noisy. Some more so than others. I've heard GS motors that sounded like threshing machines and then I've heard them (like my girls 550) that have a nice quiet sizzle as the cams work. I think they sound like a bunch of old Singer sewing machines running in unison. Aren't you up near Columbus somewhere?
 
install the cams with plasti-gauge under each journal and torque the caps to required tightness. Remove the caps and examine the squished material. If it is a uniform width and not extremely thin on one side I would say you are OK. You can also polish the journals with 400 grit on the steel and 600 grit on the caps to create a new face, just don't remove much material.

As a rule I use plasti-gauge whenever i am assembling things like this, it helps determine what the torque should be. Usually a range is specified and I start at the low end and progress up until I see the clearance is within specification.

I would install new gears and cam chain unless you can salvage the original set from the old cams.
 
Read againthere Duane I had to myself. He's wanting to use his current cams and chain and caps in a new used head. So everything except the head and valves will be fromhis bike. The only worry there then would be the bottom side of the journal bearings. I think you'll be just fine Jim honestly. Since most everything is already mated and worn together as long as the new head has no obviously different wear patterns or scoring or burs or what have you it should be just fine. Btw replacing the cam chain propperly requires splitting the cases. Not sure he wants to take it that far since he just got the thing running. Lol
 
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Buster-boy said:
Can I use cams and caps from one head on another or are they machined specifically for that partcular head?
Click to expand...

The caps are torqued down, then bored together to make a perfectly round opening for the cam to ride in. Wear has nothing to do with it. That is why the caps are labeled, A to D, and why they should not be used on a different head from the one they came in. If the original caps are gone it may be possible to measure the bore, could find a pair that line up. Better idea, a machine shop might be able to line bore the head with the new caps. Ray or someone else who does engines would know all about this stuff.
 
duaneage said:
install the cams with plasti-gauge under each journal and torque the caps to required tightness. Remove the caps and examine the squished material. If it is a uniform width and not extremely thin on one side I would say you are OK. You can also polish the journals with 400 grit on the steel and 600 grit on the caps to create a new face, just don't remove much material.

As a rule I use plasti-gauge whenever i am assembling things like this, it helps determine what the torque should be. Usually a range is specified and I start at the low end and progress up until I see the clearance is within specification.

I would install new gears and cam chain unless you can salvage the original set from the old cams.
Click to expand...


Hate to break it to you duane but you can not adjust clearance between the cam and caps by tightening the caps.
 
You can reuse everything. the only problem would would be the hold down cap for the cams That's iffy because they are machined to the head
 
Yeah I'm in Westerville (NE Columbus) near Hoover Dam if you've ever been around there. My bike is an 81 so there's only two years I can use (I think), 80 and 81, and it seems there's only like three heads for sale in the whole nation. I've used the junk yard search engines but those guys think they have gold or something. They want like $200 and up. Cripes, a few hundo more and I can buy a whole engine!!

I suspected the cables were getting a little dry and causing that noise. I know you've heard it before, but like you say without hearing it it's tough to know for sure. I'll dump some 3-1 down there next time I go out and see where that gets me.

Yes - the chain and cams chatter like a teletype. I know the chain is tight. I've had the tensioer off before and it's torqued to specs now. I tell people that's the squirrels running in the cage. LOL!!

Duane - thanks for the tips. I think I'll pass on this one and wait for a better one to come along. The way my luck has been going with this bike it'll cost me $1,000 just to get it right. I think I'll try the silicone on the plugs like the PO did. Can't hurt, right?

Plus with the colder weather coming, I don't have a heated garage to work in. I'm going to ride as long as it stays above 40 degrees, after that it's too cold in the garage to work.

I should just fire bomb this thing. It's wants to run right, really it does. I just don't have the time, money or shop to do it right.
 
Buster-boy said:
I should just fire bomb this thing. It's wants to run right, really it does. I just don't have the time, money or shop to do it right.
Click to expand...

Sell it to someone who fixes these bikes all the time.
Like me.
I'll have an 1100 engine in it in a jiffy.
 
Wow it's like hollering in a cave in here. ECHO! Echo! echo! Hehehe and actually Tom while you're mostly correct wear does have some to do with it. The line boreing may make the bearing perfectly round but the cams themselves won't be. Over time they'll be pulled and tensioned slightly out of true and as they ride in those bearings the bearings will wear to the cam. Is it a huge deal on a street made bike? Probably not. Although recently Steve and I worked on an 1100 with a broken cam. After finding the cause (the po or his mechanic left a locator dowel in the the head which got picked up by the lobe and caused it to jam and lift the cam enough to snap it at the relief cut next to the cap) we installed two used cams ( as well as did a full top end refurbish) after double checking nd triple checking our torques we fired it up and lo and behold it immediately snapped the opposite cam. Can't say as the second hand cams vs the cam caps were the cause but I don't know what else could have done that. After reinstalling the original good cam it ran fine. Odd indeed
 
Install the cams and caps in the new head and see if they spin freely.
 
Buster-boy said:
My bike is an 81 so there's only two years I can use (I think), 80 and 81, and it seems there's only like three heads for sale in the whole nation.
Click to expand...
Why can't you use one from an '82 or '83? :-k

The only thing is that you will also have to get the valve cover with the newer head, as they have 19 holes, the earlier ones only have 16. :o

I think everything else is the same.

.
 
Steve said:
Why can't you use one from an '82 or '83? :-k

The only thing is that you will also have to get the valve cover with the newer head, as they have 19 holes, the earlier ones only have 16. :o

I think everything else is the same.

.
Click to expand...

Well they're different cases for sure. The 82 and on cases look like those used on the 1000G and 1100G so I'm not sure that didn't change head bolt spacing. The oil pan gaskets and clutch cover gaskets certainly aren't the same I know that much. I'm off to chck part numbers cause now I'm curious.
 
According to the cross ref on Babbitt's, I can use 80-81G, 80-83GL. I'd never had thought the GL would work.
 
There is no reason to change the head because of a couple of stripped spark plug holes; get some timeserts installed or get yourself one of those Helicoil solid insert spark plug repair kits (not a common spring wire Helicoil type, it's a solid metal insert for spark plugs).

Regarding this bike in general, did you make sure the cam chain tensioner is properly tensioning the cam chain? You need to take the tensioner off and see if the plunger springs out smoothly and easily. To install the tensioner you push the plunger in and then snug down the set screw, after the tensioner is bolted to the engine you need to release the set screw to let the plunger back out. Many people forget to let the plunger spring back out or the tensioner itself binds up and the plunger sticks inside. I'd make sure this is not the case before you pull the entire head off.

Good luck.
 
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