Starter Clutch Replacement

Good morning,
Well, after diagnosing my bike with a damaged/gunked up starter clutch last year, I am finally working on splitting the cases to replace/repair it; whichever is necessary, though I am thinking of just replacing while I am in there. I have been taking lots of pictures, and will try to get things uploaded soon, probably once I get to the point of ordering the parts. My progress on this is very slow right now, I get to work on the bike in 15-20 minute increments or so. I brought the bike down into the basement the night that big storm hit the east coast at the end of January and I am just getting ready to take the engine out of the frame. My first question in this process is about storing the engine: Is it OK to have it upside down for a while? I am trying to do this without disturbing the top end, so I figured once it is removed, I am going to flip it upside down and work on it that way. Since I am working so slowly, it will likely be sitting like that for weeks. I drained the oil (cold) and it has been sitting open for maybe 2 weeks, so it is about as drained as it is going to be until I start. I didn't know if having all that extra oil migrate into the heads would be detrimental or not. It will likely be sitting for a while right side up once I am done too, so I don't know if that will even things out or not. Any thoughts? Also, is there anything else I should think about replacing while in there besides gaskets, oil nozzle, chain guide, etc. directly related to what I am doing?

Thanks!

 

you do have a manual correct?

 

I have the Haynes manual, I am going to be ordering the FSM as well.

 

Oil getting to the head won't hurt a thing. I had mine upside down for two months.

I think you have the list of things to change covered. Inspect everything that you have to remove along the way just to be sure you can take care of any issues now (I'm thinking of the oil pump, and oil pump chain in particular).


Be very careful when removing the bolts for the alternator chain guide. Apply localized heat to soften the thread locking compound, and go slow so you don't snap a bolt head off.

 

I second that comment re the alternator/primary chain guide. Take it slow and they'll come out as they should and save you some heartbreak and extra work along the way.

I was going to replace just the springs and metal balls within the starter clutch assembly but decided that in case that didn't solve the problem it was best to get a new/aftermarket starter clutch assembly as a whole.

My old XJ900 sounded like a can of bolts rattling around at start up. It would spin and rattle and finally catch. After the replacement it's like a new bike. Instant catch and start up is so easy.

Take it slow. One step at a time. Use thread lock when replacing the chain guide (on the retaining bolts). I also took off my oil pump and cleaned a lot of sludge and small chain guide debris from the metal filter on the pump. The old 900 must have been wheezing with oil distribution as the metal filter was about 2/3rds gunked up. Any questions...just ask. I've been there...into the darkness..and came out again wiser and with a better engine.

Problems you might face: The TORX screws (3) inside the alternator housing to remove a plate. I used a combination of heat (kitchen butane torch - I can loosen stuck bolts AND make a nice crust on a creme brûlée on the same day!) and an impact driver.

Chances are you might need to replace those torx screws because the heads will be slightly stripped during the removal process. An inexpensive item from Chacal.

Any questions...just ask!

Cheers

 

+1 on the middle gear bearing retainer torx screws.

I have an air impact, so they came right out in useable condition. One way to make them easy to remove is to carefully drill out the dimples before trying to remove the screws.
You can use medium strength Loctite on them instead of staking the screwheads, but I chose to do both.

 

All the shims must be re-located correctly during re-assembly.

The starter clutch is located in the middle of the pic linked to the hyvo chain.

Also be cautious when removing these...

And finally, the beast within...

+1.

Gary H.

 

Thanks! Maybe I will try to get some more impact driver appropriate torx bits, I don't know that the cheap $5 set I have will hold up. I'll have to get a butane torch or something as well, I was using a hair dryer for things like the boots, but I don't think that will cut it here.

Looks like we are using similar systems, Rocs, I have a ton of little baggies all labelled already; I expect the collection to grow exponentially when I finally get into the meat of things. I will do my best to reassemble correctly, I am trying to take lots of pictures in addition to bagging everything in an attempt to avoid the usual "I have the right angle for everything but the thing I need".

I was actually stating to feel somewhat confident until I saw those pictures, and now I'm getting anxiety, ha ha! So far the most difficulty I have had was actually removing the exhaust. I see lots of complaints about the carbs, but removing them was one of the easiest things to do so far (not servicing them, of course). While I'm doing all of this, I also want to take the carbs to church, replace the brake pads, shoes, lines, and tires. I don't think I am going to be able to make my goal of having it on the road by April, but I wanted to get these safety things taken care of.

I am sure I will have lots of questions, thanks for all your help so far!

 

Oh. Plastic wedges for splitting the cases. The ones that are for leveling toilets work nicely and won't damage the aluminum. work them in carefully and evenly.


No timeline. No rushing. If you get anxious or frustrated while you are working just walk away for a while, or a few days.

 

Baggin' and Taggin' is old school. Get boxes or plastic bins to organize the different sections i.e. Engine, Frame, Tires, etc. These pics are from last year when I did this. She's all buttoned up and has been a runner for a while. We'll be here to help you along the way.

Gary H.

 

Thanks for all the advice, I don't know that I would have the cojones to do this if I didn't have this site as a resource.

I have ordered a set of Torx bits and some plastic toilet bowl wedge things. I'll be looking for a torch as well, would a normal propane like one you would use for plumbing be fine, or overkill? I actually need to replace my hot water heater so i was looking at getting one anyway, it's nice to get something that is good for multiple purposes. I can't say that I have made much creme brûlée myself, but if this application calls for something more in line with that, I guess I could start, in the name of economy of course.

Oh, and rocs, what is that thing above the oil spray nozzle in the last pic? It doesn't look too healthy.

 

A regular propane torch will be fine.

The thing above the oil nozzle is a hunk of the alternator chain guide.

 

+1. If you look closely you can see where the chain started to rub against the nozzle. The nozzle is located in the second pic just in front of starter clutch under the chain.

Gary H.

 

+1. Don't forget to do this...


Gary H.

 

Thanks! I will keep an eye out there as well. I would really prefer to only do this once! At least not until another 20-30k miles.

 

OK, so I made a good amount of progress (for me) yesterday. The engine is out of the frame, and I am starting to take the alternator out (I should have done this while the engine was in the frame, I guess it would have made it a little easier). Anyway, when I took the stator out there are a few copper wires that are not covered by that redish amber stuff and some of them sort of broke off like dry spaghetti. These were around the braided wire. Does this look like an area of concern, or is it fine?

 

Imo the only real way to know would be to clean and test it once the re-assembly is done. k-moe posted a cleaner in another thread that won't harm the covering on the windings. Hopefully he'll chime in sometime soon. I used 2% alcohol and a soft toothbrush then later bought a new one from Chacal while chasing a charging issue.

Gary H.

 

Ok, sounds good. I'll have to do that then. Hopefully cleaning will help; the bike had not been charging terribly well, just based on how much the brightness of my headlight fluctuated when braking and when the turn signals were on. I was pop starting the bike every time, so I don't know how starting would have been.

 

Hopefully we can help you fix this during the rebuild.

Gary H.

 

Test the stator. The resistance between the green and the brown wires should measure between 3.6 and 4.4 ohms.

 

It's reading on the high end of that, maybe closer to 4.5; I have an analog meter.

 

Actually, looks like just over 4. I was holding the baby on my first reading.

 

Should be good then. The resistance values given are for at 68ºF and resistance increases as temperature increases.

 

Sounds good, I'll just keep an eye on it then,I guess. It's probably closer to 65 in my basement.

 

Making progress, I am almost ready to split the cases! As I was working I noticed that there is some discoloration on the crankshaft or rocker (I think) under cylinder 2 while looking through the sump cover. I also borked the lip on the middle gear output flange (once again, I think is what it is called) when I was trying to loosen it from its housing using a piece of 1x4. Are either of these things cause for concern?

 

The chip out of the output shaft flange is not a huge deal since it's not big, and does not appear to intrude into the sealing area. I would dress it with a file to remove any sharp edges, and inspect or small cracks.

The discoloration on the crankshaft near the alternator chain sprocket is unusual and does concern me. It is an indication that the crankshaft got hot in that area at some time. I would want to pull the cap from the connecting rod and inspect the lower half of the con-rod bearing. Since the discoloration is closer to the alternator chain sprocket I'd think the that bearing may not be the cause of the heat and should be OK.

The chain guide looks to be in good condition, so it is possible that it was replaced, and the discoloration is a tell-tale of someone not being very careful with their torch when heating the alternator chain guide bolts for removal.

 

That is a LOT of discoloration on that crank weight. Very odd.

 

Very. It's so localized that is almost makes me wonder if the crank was repaired. The bearing journal are did get not, but not nearly as hot as the web near the chain sprocket.

Once the starter clutch is out I'd like to see the chain moved out of the way and more photos of that part of the crank.

 

OK, I will try to get some better pictures when I get the cases split and post them here for your diagnosis. I don't really know what I'm looking at. I just thought it was odd that it would have heated up in that one spot. None of the other connecting rods display a similar discoloration. Someone getting a little crazy with their torch seems to be a good explanation, I'll hope it was that. I don't know that anyone in my family would have split the cases, but my grandfather didn't get it until the 90's. It would have been early to have needed to do that kind of work, I think, since I got it and it only had 19k on it. I did notice that the Yamabond sealing the case halves seemed to be applied a little over zealously, making me think that it wasn't factory done, but I am certainly no expert. We'll just have to see, I guess.

 

So, it does seem that it might have been the starter clutch that was to blame for my problems. But this was a good thing, because the primary chain guide was also cracked almost clean through (it came completely undone when I removed it). Taking apart the Starter Clutch assembly, the gear that meshes with the starter motor appears to be very scraped up, and the bolts that attach the starter clutch to the rest of the hub are buggered up so much I had to remove one with a pair of pliers. I have attached some pictures of the crankshaft again, with more discoloration. I wonder if this is all tied together. I have some more pics I'll upload in the next post.

 

Also, there are some little black nubs on the left in the third picture, they all came apart when I opened the assembly, do they need too be in there in any special order? I posted my oil nozzle above, looks good to me, does anyone think differently? Thanks everybody!

 

The starter clutch is one problem but it did not make your crank get hot enough to turn it blue.
Seeing that the center of the crank got just as hot as the web we saw in the first picture worries me.
I can't quite see the crank journal next to the cam chain clearly enough. Could you get a photo of it, and of the lower half of that bearing shell?

I also think it would be wise to pull the #2 con rod big end and inspect that bearing as well.

 

^ what he said.

 

Boy, this isn't the open and shut case I was hoping for. Oh well, ounce of prevention and all that. Can I just unbolt the bottom of the rod? Is that what you are asking? I just want to be sure I am prepared for when I have to put it back together if I need to do anything special.

 

Yes, you can just unbolt the bottom of the rod (the cap). Don't turn the crankshaft, and stuff a clean rag between the piston and the top of the big-end of the rod to keep the bolts from falling onto the piston. Reassembly will require a torque wrench, and if you do not have one you can borrow one from an auto-parts store.

The condition of the bearings will tell us if you have a big problem, or just a mystery.

 

Do any of these cover it?

 

Woops, got your message late. I will go ahead and do that then. As luck would have it,I have an in/lb torque wrench scheduled to arrive tomorrow! I already have a ft/lb one. Everybody loves a good mystery!

 

The crankshaft journal looks pretty good. The bearing shell is in the other case half. Go ahead and take a pic of all four individually, as close up as you can and still get a clear focus.

 

It looks like that engine might have run out of/low of oil at sometime in the dim-and-distant past. I would be kinda worried about taking that up 10K rpms............it's one thing to have a rod let loose, but having a crank break would make any day a Very Bad Day.......

 

Agreed. I hope that rod bearing will give us a definative answer. I'd expect to see discoloration at that journal too.

 

OK, here are some pictures of the lower half. I tried to take one using the nice camera, but the closest that I could zoom in was on the entire case, ha ha. It zooms in very nicely though. I took some individual pics using my phone as well.

I am at least owner number 3 of this bike, I can fairly confidently say no-one in my family ran it out of oil, I know in the about ~5k I have had it, it has had 5 oil changes, ha ha. 3 of them were related to diagnosing the starter clutch failure though. I typically ride in the 4-5k range on the bike, so if I just had to worry about keeping below that, it shouldn't be an issue. I'll try to get pics of the connecting rod bearing as well a little later.

Finally bit the bullet and signed up for imgur as I was having trouble uploading this round. So...:

Full lower case:


Left side rod end:


#1:

#2:


#3:

 

Pictures #4 and 5 (and possibly the last image, too) show some significant bearing damage. Something happened in there..........what do the upper main bearing shells look like?

 

I assume I will need to remove the crankshaft for this? Sorry,I didn't read much further than what I needed to do to replace the starter clutch.

 

Here is the crankshaft under the rod:


Now imgur is giving me crap, the rod bearing pictures are attached. The lateral scratches are from my fingernail, it does catch slightly.

 

Sorry, the rod bearing I took pics of above was #3, attached are #2.

 

The crankshaft main bearing that has the damage is the one I was worried about.
The damage to the con-rod bearing confirms the problem.
As Chacal said, it was run low on oil, or there is a blockage, or the oil pump is not putting out full pressure.
You need to make some choices.

Slap it back together as a light-duty rider (never go above 5,000 RPM), and hope the crank doesn't fail while someone's riding it (I'd even replace the damaged main bearing (honestly, I wouldn't even choose this option unless I had no other transportation (Honestly I'd rather walk))).

Find a replacement crank and the bearings that you will need to install it (you'll need the new crank first so you can do the math for the bearings).

Sell the parts and use the cash to help defer the cost of a replacement engine.

Part or sell the bike as-is and make it someone else's problem.

 

I appreciate you telling it to me plainly. I might have put it back together and just hoped it was fine, but I have too many people depending on me being alive. Plus,I usually keep it between 4-5k, but every once in a while everybody gets a wild hair! I guess I'll be looking for another crankshaft, I've put enough money into this bike to have bought another one at this point, but I'd just have to put more money into getting it where I want it with anything I could afford. This bike will ride (safely) again!

This just fits the day I've had; I just bought a new to me van today and one of the tires blew out on the way home. Grrrr.

Anyone have a spare 750 crankshaft laying around?

 

I found one on ebay: http://www.ebay.com/itm/190787871760
Does that look good?

 

Wow Gnat, you're not in the best spot here.

My first thought would be to try and find a used (from a low-mile engine, preferably) MATCHED CRANK/ROD set......that way you wouldn't be worrying about the rod bearing size compatibility issue.

My second thought would be to try and find a matched CRANK/ROD set with the crank's main journal dimensions (numbers cast onto the end of the crank) that are as close as possible to what you already have......even though you have some main bearings that need replacing, my thought (which may be completely unfounded, but.......) is that you want to keep the same "color" (size) bearings as what is already in there, that is how the case was machined and I'd just feel more comfortable ---- on the bike, on the freeway, at 10K rpm's or whatever ---- with replicating the factory specs as closely as possible.

 

Yes, but he's asking a bit much.
Do this.
Search for XJ750 crankshaft (they are the same for both the Maxim and Seca.
Send each seller a message asking for the nubers that are printed on the end of the crankshaft. Buy the one that is the closest match to the numbers on yours. Those numbers are half of the code that you use to figure what size bearing shells to use. The more of those numbers you see that are identical (both number and position of the number) the fewer bearings you will need to get.
There is no need to rush. Crankshafts sell relatively slowly.