Wrong cams??

Recently picked up a '82 XJ750RJ Seca. I adjusted my valve clearances, and as I was re-installing the cams I noticed that they have no journal under the 3rd hold-down! Also the exhaust cam has threads for a mechanical tach.

The bike has about 27k on it, and was running when I got it, but not real well. Starts right up on choke, but gets a little spluttery off choke. Revs up good with no odd noises. Plugs all look like it's been running rich.

Any ideas why she's got somebody else's cams?

 

Hmm, I just found a pair of XJ750 RJ cams on ebay. They look exactly like mine. But why would there be a hold-down with no journal? Does it even matter if I put that holder back in or not?

 

Its probably just a leftover production part that was used at the factory not an uncommon practice. Try running some Sea foam in your fuel helps clean out the fuel system before you start messing with things too much these bikes like higher rpms than most people realize

 

There is NO Journal on the 3rd "Hold-down".

That "Bridge" is there to place a Securing Point for the Cam Cover.

You should have Arrows on the Caps which Point "Outboard"

Each side has Two Bearing Caps and a Bridge.
The Placement allows the Securing Bolt for the Cam Cover to have an anchoring point.

Onne Cap on each side has a Machined "Inboard Surface" that is a Thrust Bearing Surface to keep the Cams from moving side to side.

The Cams are MARKED.
The Caps are MARKED.

Be sure you have the Cams in there correctly.
Be sure the ARROWS are all Correct and in the right direction.

 

Ah yes, I see that now. I had put them back anyway, since they had been there till now.

The cap order matters? No wonder I had to use a hammer on that one. :wink: Just kidding, I have a box with eight compartments that I use for cam caps and carb parts. Put 'em in the box just like they were on the engine and put the box somewhere safe. AND take pictures before starting, AND check markings...

 

yeah, I chuckled a bit when I saw the worm for the tach on mine. Either left overs as said or it's the same shaft blank as in another bike with likely a different cam grind as the final operation that makes them unique. Economy of scale. WAY cheaper to produce twenty of one thing than it is to produce ten of one and ten of another.

 

MADPHIL where do you hail from?

 

MADison WI.

 

You pulled the cams to adjust the valve clearances? You know that wasn't necessary, right?

 

Can you get the shims in and out without removing the cams on these bikes?

 

Sure can: http://xjbikes.com/Forums/viewtopic/t=14827.html

 

either way is valid so long as you zip tie the chain to the sprocket to keep timing. not having to pull the cams is about the only advantage to shim over bucket vs under.

 

I think not having to pull the cams is a BIG ADVANTAGE like if you miscalculated on one shim...

 

I prefer removing the cams. For any out-of-spec valves I remove the bucket, pop out the shim, and put both in a labeled baggie (one for each valve). I then head over to my favorite bike shop and swap shims from their shim bank for $3 a pop. The mechanic and I mic both old and new shims. Even the ones with visible markings can be off. Then I test-fit the "new" shim in the bucket to make sure it seats all the way. I've come across a couple that didn't, which really screws up your clearance calculations.

For something that needs to be done so rarely I don't mind pulling the cams. But then, I don't mind going to the dentist all that much either so maybe it's just me.

 

I guess it comes down to your definition of "rarely" or, how long it takes you to put 5000 miles on your bike.