wont turn over with electric or kick start, turns over fine by hand

I bought a 650 about 9 years ago. It was in rough shape. I rebuilt the engine, cleaned the carbs, and all was good for a 4 years. One day the bike died, the pickup coil had melted. This prompted me to buy a boyer ignition system. While I was mucking with the bike, I decided to finally take care of two problems that the bike had since I bought it; an extremely worn main crank bearing (causing a wiked rattling noise) and a slightly warped lower case (caused a slow and oil leak from the side engine cover). I picked up a used engine, tore it apart, and found that all the bearings in the lower end looked to be in good shape. I used the lower end from the used engine with the good top end from my original engine and put the bike all back together.

I tried to start the bike but was not able to get it to start. The engine seemed to bind up. I tried both the electric starter and the kick starter. Both have the same result. If I step on the kick starter, it goes about a 1/4 of the way down then stops traveling. At that point, I can put all my weight on it and it wont go any further.

I took the spark plugs out, tried starting it, and the problem persists so I don't think its a valve or compression issue. At this point, I am not even far enough along to worry about the ignition or fuel.

I can however turn the engine over slowly by hand. By this I mean I put a wrench on the bolt a the end of the alternator and I am able to turn it by hand, albeit slowly, all the way around without feeling any resistance that is greater than normal. Maybe the issue is related to the starter, or maybe its related to trying to turn the engine over quickly, since it turns over ok at a turtle's pace.

I tore the engine apart again and separated the lower engine case, optimistically hoping to find a broken gear or something obvious. The upper end looked great, no scoring on the cylinders and the valves look good. I cant find anything wrong with the lower end. The crank seems to turn freely and the transmission spins without binding up at all. That was all 4 years ago. I have another bike and plenty of other projects. I just now finally got back around to trying to troubleshoot this engine issue.

I am out of my league with troubleshooting this problem. I have everything apart and I have an entire spare parts engine. Is there anything that I should focus my attention on? Anything that might cause this kind of issue?

Thanks.

Edit: I realized I forgot to mention, its a 1981 xs 650 special.

Welcome to the site! I don't have any ideas for you but you came to the right place. Some of most knowledgeable people from all over the world on the Yamaha 650 twin are members here. They should be able offer some suggestions.

nezzer said:

I decided to finally take care of two problems that the bike had since I bought it; an extremely worn main crank bearing (causing a wiked rattling noise) and a slightly warped lower case (caused a slow and oil leak from the side engine cover). I picked up a used engine, tore it apart, and found that all the bearings in the lower end looked to be in good shape. I used the lower end from the used engine with the good top end from my original engine and put the bike all back together.
Edit: I realized I forgot to mention, its a 1981 xs 650 special.

Click to expand...

- what was the donor motor?-engine nr

- when replacing the bottom end, and warped casing, did you replace both upper and lower cases together-they are a matched pair and should have the same code stamped into them...like this



- has the kick start mechanism been installed correctly?

- on the centrestand, chain mounted, plugs out, does the back wheel turn in neutral?...what about the other gears?

- Donor engine was also from an 81.

- Yes, both upper and lower case halves from the donor motor were used. The stamped numbers match.

- The kick start was installed correctly, at least the portion that just pulls out when the side cover is off. The symptoms were the same with the kick or electric start.

- Yes the wheel spun freely in neutral. It did not spin freely in first. I did not try rotating the crank with the engine in gear. I did not check any other gears.

- were the donor cases separated?...and the gearbox checked?

I did separate the donor gearbox to check the internals. They looked good at the time though I must have missed something. The case is currently separated. I am not sure what to look for on the tranny. I dont see any broken teeth or excessive wear. Other than that, is there anything I should look for?

Did you try to turn the engine over with the clutch assembly removed? Did removing the top end make a difference? If the bind wasn't created there, did the motor free up as you relieved torque on the cases? Sometimes when you can't find an obvious defect, you can track down the problem through elimination.

I did not try turning the engine over with the clutch removed. I didnt think to remove it, refill with oil, and try turning it over. That is a good idea.

I think what I will do for now is take as many innards out of my original bottom end and transplant them into the donor bottom end, reassemble, and see if the problem persists. If it does, I can try a few more troubleshooting steps to narrow it down.

You needn't refill with oil just to turn the motor over and see if you've freed the bind; just drip a bit of oil or top lube into the cylinders if you're concerned. If you check for resistance at each step of the assembly process, you'll find the problem.

Well I started putting everything back together, testing components as I go. The transmission looks good. I selected gears by hand and everything turns as expected. I also checked the gears that link the electric starter to the crank and everything looks good. Perhaps my problem is outside the case on the bottom end, i.e. clutch related. I didnt finish putting everything back together and it will probably be next weekend before I can work on it again. I will report back my findings.

Well I got back to working on the bike more. I ended up taking the gear selector assembly (forks and all) out of my original engine and putting it in the donor engine just because I am supersticious of that donor engine. I am pretty much at the point of just using the case halves and the crank, the rest of from my original engine. I have the case halves back together and have been testing things as I go.

I am having an issue with the clutch. I am trying to put the clutch assembly back on the right hand side but whenever the clutch boss nut is tightened at all, the crank stops rotating. For starters, I have been following post #7 in this thread, which explains the order which all the clutch stuff goes back together. I am going to shamelessly highjack the clutch diagram:


One thing I am not clear on in that post is the exact order of washers A and B. The diagram seems to indicate that this is the proper order:


When I do that, I end up with the spacer shaft (c) sticking too far out, resulting in the final washer (g) inside the clutch boss resting on the top of the spacer shaft (c) rather than on the roller bearing (f) shown in this photo:


Obviously this defeats the purpose of the roller bearing. If I switch washers A and B, as shown below, then everything lines up and roller bearing ends up supporting the load:


With that arrangement of washers, bearings, etc. the clutch boss and clutch housing both rotate freely (although independently) with minimal effort. There is no excessive resistance spinning either the tranny, via the clutch boss, or the crank, via the clutch housing.


The problem comes when I torque the clutch nut (k) to 55 ft lbs as specified. Once torqued, I can barely get anything to turn. I am certainly not able to get anything to turn by hand. I can barely get anything to budge when using a wrench.

Is my clutch setup messed up? Is there something else that might cause this? Presumably, this is the exact thing that prevented my engine from turning over originally.

Thanks

- the correct order is

So I presume that "first washer...25.2-36-1.0" means that the first washer should have a thickness of 1.0.

With that the arrangement the spacer sits too far into the clutch basket which prevents the boss from turning nicely on the thrust bearing. Instead it turns on the (washer...25-50-2) which is resting on the top of the spacer rather than sitting on the top of the thrust bearing. That leads me to believe I have something wrong still.

Here is a picture of all the washers etc that I have:


Hopefully my problem is just related to the washer order. Still, I dont understand how the boss can be torqued down to 50 ft lbs while still allowing the basket to turn freely. The boss will press on the basket which in turn will press on... a washer? What allows the basket to turn freely. All I see is the circular bottom of the basket (the part with 4 dimples in it) turning on a washer that is sitting on a washer. Does that arrangement still spin with 50 ft lbs of torque on it?

- most of the pressure should lock down on the spacer-C-in the above breakdown...the one that fits inside the basket

- first washer...

- it shouldnt sit on the outside of the bearing

- second washer...external diam...50.0mm

Your saying, going by the diagram

inxs said:

- the correct order is

first washer...25.2-36-1.0​

second washer...25-50-2​

spacer​

basket​

washer...35-51-0.5​

thrust bearing​

washer...25-50-2​

boss​

Click to expand...

A - first washer 25.2-36-1.0
B - second 25-50-2
E - Washer 35-51-0.5
F - Thrust bearing
G - Washer 25-50-2

25.2-36-1.0 - First no is internal diameter 25.2, second is the external diameter 36, and third is thickness 1.0

Just got out my dial caliper to measure all the parts.

I have two of these:
25 - 50 - 2

I have two of these:
35 - 51 - ~0.5

I have one thrust bearing:
35 - 51 - ~1

It looks like I am missing "A - first washer 25.2-36-1.0" and instead have a duplicate of "E - Washer 35-51-0.5". I did have two clutch assemblies at my disposal so I may have mixed up washers the last time I was in there.

The dimensions of the "A - first washer 25.2-36-1.0" makes me thing that it sits against the inner part of the tranny bearing. If thats true, than that might answer my question as to how the clutch boss can still spin when torqued to 50 ft lbs.... without that smaller washer in my setup the clutch boss was putting pressure against the OUTER part of the tranny bearing, which does not spin. With the smaller OD washer, the pressure would be put on the inner part which does rotate with the clutch boss.

It looks like BikeBandit has that washer for sale, thankfully. I will be ordering that now and fitting it when it arrives.

On a side note, while measuring the washers, I noticed that one of my E washers was cracked all the way through. You can't tell unless you twist it, then it starts looking like a lock washer. I guess I am lucky that I have a spare then

This is very informative.

- if you look at washers a and b, they sit under the spacer between it and the bearing, the smaller diameter one sitting directly on the bearing inner
- washer e and thrust bearing f slide over the spacer and sit on the basket
- washer g sits on top of the spacer, between it and the boss

- hope this gets you going

Obviously many PO's have had these clutches apart and do not put the correct washers back into place. I had my clutch apart just to check for wear (none found), but I did find that the "A" washer was missing................I guess the last PO didn't think it was necessary I got a replacement washer from Yamaha. The clutch basket had been rubbing on the primary drive gear washer.

Just pay attention to the size and thickness of the washers in the drawings and your clutch will work fine.