Starter Clutch Replacement

OK, this one is cheaper and the rods say G4, which are what mine say. I am going to read through the write up on the XJ4Ever site, I glanced at it earlier and saw there are a few pieces to consider.

 

OK, I have searched over ebay and have sent out the requests for information.

Based on the few that had all the information visible, it looks like I will need to replace at least a few of the bearings, both rod and main journal. Can I swap good ones around as we do for the valve shims as long as they are of the same type (e.g. main journal vs rod, oil holes vs not)? Based on the pictures I have uploaded, do any of them stand out as needing replacement? I assume that any gouges that I can feel with my fingernail will necessitate a replacement?

Thanks!

 

Rod and main bearings are NOT interchangeable.

On crank bearings, the lower bearings MUST have the 3 oil holes in them. The upper case bearings can use either the holed or hole-less main bearings.

On rod bearings, the bottom (cap) bearing does not have an oil hole; the upper (rod beam) bearing may have an oil hole or may not. IF the rod BEAM has the drilled passage for the oil spray (onto the cylinder walls), then the upper rod beam bearing must have an oil hole. Otherwise, the upper bearing can be hole-less, too. We're sure that all of XJ750 (air-cooled) engines used rod beams with oil spray passages (thus requiring an upper bearing with the hole), but are not sure on the other models.

I would NOT recommend swapping bearing shells, even though it "may" be okay. Bearing shells develop wear patterns in them based on where they were mounted and used, and one rod (or main) bearing's wear pattern, EVEN THOUGH IT IS THE SAME "SIZE" BEARING AS IN ANOTHER POSITION, will not be the same and might cause premature oiling/wear issues.

 

Chacals warning about moving bearing shell position has merit, however if the shells maintain the correct clearance, and there is no scoring (run your thumbnail over them. if it catches on the bearing surface then discard the bearing), they can be swapped around. any bearings with scoring that is in any way perpendicular to the direction of crankshaft rotation should be discarded. Visible scoring that does not catch your thumbnail will not effect oiling, but would cause me to not use that bearing for a position swap.
Ideally you would want to use all new-bearings, but that can be cost-prohibitive.
You will need to verify bearing clearances with plastigauge and a dry assembly of the rotating bits.

 

Is there a published list of what the clearances should be? I see the different color codings, but not how to know when to move to a different size.(other than based on the numbers on the crankshaft, case, and rods. I don't even see where they mention the actual size of the shims, just the numbers and their corresponding colors.

 

The bearing sizes are not listed in anything other than color sizes; it's just how Yamaha did things. I think the goal was to make production run smoothly (colors are easier to remember than decimal values, and therefore more difficult to mess up). The bearing to bearing journal clearances are listed in the service manual.

 

i looked at those pictures several times and i just don't see a problem. The crank got hot when that gear was heat treated at the factory and the bearings show very little ware. How many miles on it?

 

The chain sprockets did not get heat treated seperately from the rest of the crank. the crank would warp if it had. Nothing on the crankshaft should be that color.

The upper #2 main bearing is absolutely roached.




That uneven reflection in the second picture is the telltale of a worn out bearing, and it's full of crap (the black flecks) and gouged all to hell.

 

K Moe, is that what they refer to as main bearing oil clearance?

Polock, it has just under 25k on the clock.

 

from looking at the colors, the sprocket was the hottest part, heat treated to be a sprocket

 

Look at photos of other crankshafts. They do not have localized discoloration unless they were overheated. The whole crank gets heat treated in a big oven, not with localized application of heat.

 

yes.

 

ok, i did. now what

 

What would cause that kind of "over"-heating (discoloration) effect in just that one area?

I've never noticed it before (but I don't handle a lot of cranks) but I guess it is somewhat common...........

 

Polock, I did see several of them that had similar bluing to mine, I just assumed that they were bad as well. There are more of them that don't have that discoloration, so it seems that one of the two is wrong, and I assumed it was the blue ones. I looked around and didn't really see much as to whether or not it is actually bad. I think that if it was just the web, or just the web and sprocket,I might be less concerned. But the fact that the shaft itself is discolored kind of clinches it for me. I'm no mechanic, and I don't have much experience with this stuff, so I rely on the experience of those on this forum. I looked up the temperature that the rod would need to get to in order to change to blue (assuming the rod is steel) and it is around 590 degrees Fahrenheit. Do we know how got these things normally run? Once again, no idea really, but that seems on the high end. I want to think it would be ok, because I really don't want to dig in to the top end as well, but I don't knew if that is worth the risk. Would you run with it?

 

OK. I looked at photos of a NOS crank for a 750.



I see bluing.
I am wrong about the crank.
I do still reccomend that the #2 main bearing (and likely its mate) should be replaced.

Now....how does a poor amn come up with $300 to buy a NOS crankshaft.....

 

i wouldn't think twice about using it.
they probably use induction heating there to harden the teeth on those sprockets for wear purposes. and some heat leaks over to that web.
if it got to 590 deg while it was running, wouldn't oil be burnt on it? not all nice and shiney blue color
i don't think i've ever read about a broken crank here
here's a good bearing and a really shot bad bad bearing, if yours look even a tiny little bit like the bad ones replace it
http://www.dansmc.com/bush_plain_bearings.htm

 

Thanks, k-moe and Polock! I figure on replacing at least number 2, probably a few more. Am i right in assuming I'll have to remove the cam chain to lift the crankshaft up enough to check, or is there a way to get enough play in it somehow? Maybe just removing the tensioner?

 

You will have to remove either the cams, or break and replace the cam chain with a new one. The crankshaft accounts for almost a third of the weight of the engine. Just lifting it up a bit to sneak a bearing shell out isn't going to happen.

 

Would someone be able to verify what the part attached is? I believe it is the intermediate idler gear. It looks to me like it should probably be replaced, any thoughts there?

 

what seems to be wrong with it?

 

It looks like the 3 billy's that were loose on the starter clutch really tore it up. Maybe the picture below is a little better. The difference in color between the front of the sprocket and the back makes me think a layer of metal got eaten away or something. The front had that flat brown color, while the back has the shiny chopper color around the teeth and then the silver color underneath. The back just seems chewed up too, the pictures aren't quite capturing it. Should I maybe just try to smooth it out if I can and call it a day?

 

The surface that the rollers ride on is the important part. I've done two of them and neither one was perfect but after new springs and rollers they worked fine.
Look at the part the three springs go into for cracks.
If you want to hit the teeth with a wire brush, ok but don't get any more aggressive than that

 

Run it. It's fine.

 

Awesome, will do, thanks!

 

OK, finally got the camshafts out. I was looking at the chain guides for the camshafts and was wondering if I should consider replacing the one on the intake side. The other side looks like it has plastic still on it, but this one appears to be down to metal. I am not sure if that is normal or not. Any thoughts?

 

Replace them you are this far into it

 

It's been a while since my last update, things have been busy, but I just finished my final paper for my current class. While I have a little bit of free time I am trying to get back on track and I got new main journal bearings all around (found them for under $10 apiece new!). Looking at the service manual, it says to apply molybdenum disulfide to the connecting rod bolts before re-installation. I don't have any pure moly, but I do have the following two products, would either of those be sufficient?

and

Valvoline's Synthetic Grease - Formulated to provide superior high and low temperature protection. SynPower Synthetic Grease is an excellent heavy-duty and multi-purpose automotive and industrial extreme-pressure grease. SynPower is formulated with a lithium complex thickened in a synthetic base oil, moly and other premium additives to provide superior protection from high loads and extreme temperatures.

Also, is the above Valvoline product good for re packing the rear wheel?

 

that Valvoline is what i use, seems to be good stuff

 

Ok, engine is pretty much ready to be put back together, I just want to get a set of oil seals yet so I have replaced all the rubber and plastic parts. In the bottom end.

This week was spent bleeding the brakes, I got new stainless lines and pads from Len. Man, that was a bear! I just started tearing into the carbs last night, and I've got a question already: the float needle seat on carb 1 (the only one I've gotten into so far) doesn't have a gauze screen on it, is that an issue? I have Rick's carb write up, the church of clean, Haynes and FSM , it looks like some don't have them, but Haynes has a picture of the seat with gauze.

I wanted to do the carbs before putting the entire back together so I can just do 1 more big order. I assume that, just by virtue of having started doing this, I should replace the float bowl gaskets? They look pretty well attached, so I may have to do some more scraping (as if I didn't get my fill of that with the engine covers etc.). I'm going to do the throttle shaft seals as well. I'm going to get new hardware too since almost all of the screws are deforming in some way as I remove them. Pilot and main jets too, unfortunately, I almost got a piece of brass in my eye when a chunk of the head came off. Yee haw.

 

a lot of people toss those little screens and just use a inline filter. that way you can see any junk it caught

 

Good stuff, I am running an inline filter, so I won't stress about it then.

 

Well, I have gotten carb bodies 1 and 2 cleaned up, and ready to reassemble. I know it isn't the most time effective way of doing things, but with how long this has been taking I want to make sure I have a visual reference to consult when putting them back together, so I am doing one at a time.

Going through things in preparation to order everything I need to button it back up, I see that this bearing by the middle drive has a shim attached to it that looks like a half moon. I was wondering if that should be a full circle or if what I have is correct?

 

That is a bearing locating shim. It's a half moon and is oriented correctly in your photo.

 

Great, thanks!

 

So, I'm working on the carbs and trying to put the first one back together after the carb dip, ultra sonic cleaning, probing, etc. And when putting the float and needle back in, the rubber tip of the needle fell off. What is the likelihood that using superglue or something to that effect would be sufficient to repair that, or do I just need to suck it up and buy new ones? The money train is running out of steam...

 

Just pop the rubber tip back on. They fall out sometimes when dropped. No big deal; that won't happen when they are in the carb.

Just be sure that the needle seals before you put the carbs back on the bike.

 

Great to hear, thanks!

 

Does anyone know if alum will work to get the carb bowl drain screws out? I was only able to successfully get one out, the rest are being really stubborn. I have been soaking them in pb blaster for weeks, trying occasionally to remove them, using heat as well. The heads of the screws are pretty much at the end of the line.

 

Drill clear through the screws to release some of the tension on the threads.
Follow up with heat and an extractor.

Alum should work, but I'd still drill through them to speed up the process.

 

Replace them with some of Chacal's nifty stainless steel Allen head screws They are awesome!

 

Ok, I'll give that a try. Already got the full hardware kit from Chacal, Nuch! Not quite as bling as some of higfiddles' masterpieces, but I'm pretty happy with how this is going do so far.

 

So,I got through the first two, easy peasy. Unfortunately, on number 3 the extractor snaps in the head.... I used a drill bit to drill on either side of the extractor tip so I could use a screwdriver to turn it out. After a few tries it worked! Might be buying a lotto ticket tonight.

 

You got lucky!

 

OK, I am working on putting the cases back together finally! I got the oil seal set from Len and I had some questions on installation. I couldn't find anything in the books about whether or not I should be using something when putting them in, be it oil or grease of some sort. I replaced the shifter shaft seal on my wife's bike and just used oil when pressing it in, and it seems to work, but I am a little more nervous about the middle gear output shaft and crankshaft, since they will see a little more constant motion. Is just using some motor oil on them, then pressing in OK? Also, I noticed in cds1984's writeup, he had whatever sealant was being used around the crankshaft oil seal and blanking plug, should I do that as well? I have some Loctite 515 for the job, if that makes any difference.

I know where the rest of the seals go, but I have a question on the two middle gear seals:
middle driven sleeve gear output shaft oil seal
middle gear output shaft oil seal

The middle driven sleeve gear output shaft oil seal is the one pictured below peeking out from behind the flange (I think), does the other oil seal go underneath the bolt holding the flange on in the picture? I looked at the parts diagram, and it is listed as an o ring, but I can't find another oil seal in reference to the middle gear.

 

Yes on oil or grease on the oil seals to prevent them from tearing during instillation.
Yes on the 518 in all areas where case sealer (Yamabond) is called for (including the crankshaft seals).

The o-ring on the output shaft is under the nut and washer on the outboard side of the shaft. The oil seal is the black bit behind the flange that seals the output shaft itself.
There is also a large o-ring/seal that goes between the output shaft bearing housing (the part held on by those bolts) and the case.

And that question brings up a question of my own (since the answer is in the service manual). Are you doing this without a service manual? The case bolt torque figures and sequence is not in the writeup, and you better had to that all correctly or the cases can warp or fracture.

 

Sounds good, is 515 ok? I've seen both 515 and 518 recommended.

 

+1. THIS IS VERY IMPORTANT:

Also...a light smear of sealant is required as directed at the bolt holes above the crankshaft bearings. Too much sealant might work its way to plugging a oil lube hole for the shaft.

Gary H.

 

Pardon the mess but, yes, I do have both the Haynes and fsm I am working off of. I have made sure to use the tightening sequence when checking the bearing clearances using plastigage. The manual just didn't say much about the oil seals. I did see where the oil seal I had pictured was, and that you describe, but not the other one. Looking at the parts fiche, it looks like that might be at the other end of the final drive. I'm sorry, I know some of the questions I ask have answers in the book, sometimes it isn't explained just right for it to click for me.

 

Thanks! Right, it should be 2-3 mm away, per the manual (to my memory).