Messages

1

Technical / Brake shoe lining and Crankcase cover leak

« on: June 27, 2011, 07:25:18 AM »

Is there any way to reattach a brake shoe lining to the backing plate? the linings on my yz 100 came off and it looks like they were held on before by some type of glue, there weren't any rivets.

And since I got a new post started, I also have a crankcase cover leak coming from were the cover and rankcase meet, right at the gasket. I've looked all over and have been unable to find the torque specs so when I put the cover on I just snugged up the bolts and have been working my way up in torque if it continues to leak. Now they're pretty tight and the leak still hasn't stopped. The bolts are the socket head cap type and I think they are M6. Any help is appreciated, Thanks.

2

Technical / Re: YZ 100 Fluids

« on: June 22, 2011, 06:40:27 PM »

Thanks for all the help. I've never heard of this motul stuff, I wouldn't mind giving it a try but I doubt there are any stores near were I live that sell it.  So as far as the fuel goes, will the 25-1 Lucas mix I mentioned earlier work? should I change it after the engine is broke in-maybe like to 32-1? 

3

Technical / YZ 100 Fluids

« on: June 21, 2011, 07:59:15 PM »

I'm finally coming to the end of my 78 YZ 100 rebuild (btw, thanks to all who have helped, it was very much appreciated) Anybody have any sugestions on what kind of oil to out in the transmission and fuel mix? I've heard of people using 10w-40, 85w gear oil, and even ATF for the trans as long as what ever they used is a good quality and is changed often, the same would apply to my 78 YZ wouldn't it?  I'm running a 25-1 fuel to oil mix in my other 2 strokes (using Lucas semi synthetic 2 cycle oil) can I run the same mix in my YZ? I know it varies depending on what type of oil used. Any help is appreciated, thanks

4

Technical / 78 YZ 100 bolt torque specs

« on: May 29, 2011, 07:15:18 PM »

I'm rebuilding a 78 yz 100 and was wondering if anybody knew the torque speces for the following: bolts for crankcase halfs, nuts holding cylinder to crankcase, and the nuts that hold the cylinder head to the cylinder. I would go ask a yamaha dealer but there isn't one near me.  Thanks 

5

Technical / Re: YZ 100 Rebuild: Bad Crankcase???

« on: April 20, 2011, 11:18:02 AM »

Thanks guys for all your help. It wasn't until I had the cases split that I noticed the problem, so they are already apart, just like in the pictures I tried to post.  I included a link to each picture just in case anybody wants to go back and see them.  I just got a dumb question, due to the crack going all the way around, the whole bearing moves.  Should I just tell the machine shop to center it before they weld it or am I going to have to assemble the crank cases with the crankshaft and then somehow mark the position?

6

Technical / Re: YZ 100 Rebuild: Bad Crankcase???

« on: April 19, 2011, 08:20:35 PM »

Here are some pictures of it.  On the inside the crack I mentioned is clearly visable, on the outside there appears to be 3 globs of J B around the seal.  I plan on having it welded if there is no other way to fix it.  Will welding it ruin the bearing and/or seal? If so how can I remove them without damaging them? Thanks  
Links
http://imageupload.org/getlinks.php?s=1daacd339ba41f0ad32a5c71a8542ed2
http://imageupload.org/getlinks.php?s=de0fee9d993e3f565a6ce8bad96ae33b
http://imageupload.org/getlinks.php?s=a3728006e28756d1bc1ac90f5deeb591
http://imageupload.org/getlinks.php?s=21570d8fa4d7060727d0a6661653ffdd

7

Technical / YZ 100 Rebuild: Bad Crankcase???

« on: April 18, 2011, 08:45:11 PM »

I took got a good look at the right side(side with clutch) of my 78 yz 100 before starting to assemble the motor and noticed a problem with the bearing for the crankshaft.  The bearing itself is ok but the chunk of aluminum that the bearing is pressed into is not attached to the rest of the crankcase.  There is a gap between that piece of aluminum and the rest of the crankcase all the way around that's big enough to put a piece of paper into. It can move a little but will not slide out.  On the other side it appears that there were 3 holes that were filled with J B weld.  Anybody got any ideas what is going on with this?  I will post a picture latter if needed.  How should it be fixed?

8

Technical / YZ 100 Rebuild: Crankcase gasket?

« on: April 09, 2011, 08:32:34 PM »

Ok I'm running into some more small issues rebuiling my 1978 YZ 100.  The trans was stuck so I split the case and discovered 2 out of the 3 shifting forks where stuck.  The problem wasn't getting them unstuck, the problem is trying to find a new crankcase gasket.  I've looked on the internet and found the crankcase cover gasket, but not the gasket that goes in between the two sided of the cases.  The cases look like they were sealed with sometime of silicone when I pulled them apart.  Anybody know were to get a crankcase gasket?  If not what can I use to seal it back up?  Thanks

9

Technical / YZ 100 Rebuild: Bore Size

« on: March 24, 2011, 09:36:01 PM »

I'm currently rebuiling a 1976 YZ 100 and have already determined that I'll need a new ring and probably a piston.  I'm just having trouble figuring out what size I need.  I measured the bore of the cylinder- 51mm and even though I measured several different spots and got the same measurement it appears to be egg shaped.  Even if it isn't egg shaped I haven't been able to find the cylinder to piston clearences on the internet and so haven't been able to determine the size of piston and rings I'll need.  If it isn't egg shaped what piston size will I need?  Anybody got a chart or just know what bore is needed for each or any size of over bore pistons?(.5mm over to 2mm over)  Is there 0 clearence between piston and cylindar?  Thanks