Top End Rebuild

Retiredgentleman · Posted: November 24, 2008, 1:42 am Post subject: Re: Top End Rebuild

wrider;
No grinding been done on the head. There's some nasty ridges in there. My son has a dremel tool, so I could try some smoothing.

xsjohn · Posted: November 26, 2008, 12:03 pm Post subject: Re: Top End Rebuild

RG.......Got the Head Gasket......Thanks for sending it along........Not a factory Yamaha gasket though....looks to me like the head on yours has been off before.....might answer some things there.......

xsjohn

Retiredgentleman · Posted: November 26, 2008, 2:21 pm Post subject: Re: Top End Rebuild

Yeah John, I knew the PO had the head off, and didn't torque the studs correctly(causing huge oil consumption!)................no wonder POs are a despised and loathed group. We should tar and feather a PO each week, just to make an example of them.

xsjohn · Posted: November 26, 2008, 2:36 pm Post subject: Re: Top End Rebuild

1 a week won't even be noticed from what I have been reading lately.... Laughing

xsjohn

Retiredgentleman · Posted: December 28, 2008, 5:54 pm Post subject: Re: Top End Rebuild

Took a look at the Tach drive to-day and found a few problems. 5twins and jimmer had mentioned about the possibility of missing shim washers at the end of the drive shaft. Sure enough, there were no shims! Because there was no shim, the end of the worm gear was acting like a drill bit and slowing drilling into the casing! I measured the axial end play and it was .059" Shocked

. This would explain why I would occasionally lose my tach indication, because the drive shaft was slowly getting further away from the cable square end.

Also found that the bolt that screws into the hole in the sleeve is now to short. Rough handling by PO's had mushed the end of the screw. The screw is now about 1/2" but needs to be closer to 5/8" in order for it to protrude into the hole in the sleeve. I'll get another longer screw to replace it.

I'll also need to search for some shim washers that will add up to maybe .050" or more to remove that excessive axial end play.

Oil seal was also worn out.

jayel · Posted: December 28, 2008, 10:31 pm Post subject: Re: Top End Rebuild

not floating around in the lower end is it RG? it's fairly thick (machine washer) and has a slot acrossed it for oil I guess wouldn't want to run it thru any gears

Retiredgentleman · Posted: December 28, 2008, 10:44 pm Post subject: Re: Top End Rebuild

jayel;
I've been looking for it, but I suspect it's long gone. I know those pesky PO's had the side cover off before; clutch springs have minor damage to the screw heads, and bottom allen bolts for engine case did not have copper washers.

jayel · Posted: December 28, 2008, 11:24 pm Post subject: Re: Top End Rebuild

yeah most times it gets to one of the magnets (drain plugs or sump filter) ask around and get the proper part like I said it's fairly a thick machine washer

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Guys,

I reckon that this is a more common and complex problem that you might think..

this.."didnt torque the head nuts properply" syndrome that causes oil from the gallery to leak into the combustion chambers?

There is something going on here. It seems to be common on these bikes. My bike still smokes from cold. Even though I know the torque is good.
The guides are good etc...

What gives I wonder..there is something happening here..

xsjohn · Posted: December 29, 2008, 12:09 pm Post subject: Re: Top End Rebuild

Was this a fresh top end....or just a put together.......the seating may not be complete...........I have some ideas on seating if later the problem persists......say after 1000 miles.......

cold oil would be harder for the engine to clear from the cylinder walls....especially 20-50 in the winter.........

could torque to 35 lbs "max" starting with the ones in the center a bit more bringing them all the 35......new head gasket will squish a bit requiring retorque...even 3 times sometimes....have always done mine that way.......

xsjohn

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

My top end was redone after 300 miles, still smoking from cold.

Then re-done after another 600 miles, still smoking from cold.

With me trying to chase down this problem.

Its odd..Bike runs 100%. Strong.

Leave it ticking over from cold and it will start to smoke and then clear.
First top end rebuild after 300 miles (after original rebuild) revealed oil leaking in from central gallery.

Second time I used a smear of sealant (not my usual Loctite blue as they were out of stock of that!) and I found that studs were different lengths so I add spacers to make sure nuts were not bottomed out...

Funny also is that if left long enough the oil that leaks IN..drains through rings and doesnt smoke. Left over night it will smoke.

xsjohn · Posted: December 29, 2008, 1:46 pm Post subject: Re: Top End Rebuild

Did you lightly hone or sand the cylinder walls before re-assembly.........if not it can take forever to break in........been there and done that..........again cold starts the oil is thick and the rings can't pull the oil off the cylinders fast enough till it warms.......would give it some time ......then if not resolved I have a fix if it's a ring seating problem........

xsjohn

Retiredgentleman · Posted: January 5, 2009, 12:16 am Post subject: Re: Top End Rebuild

xsjohn had suggested putting some dimples on the clutch push rod and worm gear bolt. I'm also replacing the 2 small push rods with the single long push rod. So, today I added some small dimples. Won't know how well it works until spring riding season.

xsjohn · Posted: January 5, 2009, 12:29 am Post subject: Re: Top End Rebuild

Will be interested in your test ......with mine I replaced the entire clutch (65K) with a clutch from a 79 at the same time I did this....mine is an 80.....changed bushing and usedthe long rod too....now the clutch is way out on the end of the lever and neutral is easy........totally different than before....with no draging at all.......

Did notice that the mark on the rod before I did the indent was larger than would occur if the ball was remaining centered....would indicate the rod was wobbeling.....would wear out the bushing making that situation worse as itwent along......indent should cure that.........we will see after a few more tests if it makes any difference.....would be nice if that was the fix for crap clutches............which I had but not now........surely couldn't hurt anything........if not....

xsjohn

xsleo · Posted: January 5, 2009, 11:03 am Post subject: Re: Top End Rebuild

rg the shim on the tach rod, accorrocding to the yamaha website parts list says the shim is 8.3 mm inside diameter 12 mm outside diameter an 1 mm thick. i was putting the bottm end of my 75 together. i thought i'd check things out. comparing the parts out of my 82 engine, using the parts that look better. the 82 engine was missung a shim. the 75 had one. it was worn down to .675 mm almost 1/2 as thin as a new one. i measured the end play without a shim, it was 1.753 mm. so even with a new shim it would still have better than 3/4 mm endplay. i found some washersthat had the right size center hole, put 3 on a boltspun a nut down to hold them tight, put in my drill press to spin it. used my angle grinder to grind the washers down to the right outside diameter. then took them off the bolt and slid them back and forth on a file to remove the burrs and get them thin enough to give me just a little endplay. i didn't measure, just pulled and pushed on the tach shaft to see how much play it had. the shims i made are about .055 - .060 thick. i don't think that the shaft ground in to the cover, i think that yamaha ground the cover like that to have a flat place, square to the tach shaft, so they had a place to put the shim. both my 75 and 82 covers look like that. on the 75 the bolt that held the piece into the case was bent very badly, i think it got bent when i had to really grunt with a big pair of pliers to get the cable loose. so your po may have broke the end off getting the cable loose. when i hook the cable back on, i won't tighten it quite that much. xsjonh i think your dimpleing the clutch pus rod is a good idea. my original 75 rod was dimpled, probably just wear. i replaced the rod because the rod was all chewed up from the chain getting way loose and hitting the rod. i will try putting dimples in the new rod. my shifter shafts were bothe reduced in size where they lineup with the sprocket. so i think i can use an 18 tooth sprocket with out grinding it more.

Retiredgentleman · Posted: January 5, 2009, 4:54 pm Post subject: Re: Top End Rebuild

leo;
Yes, it pays to look around for missing parts when the engine covers are off. It's almost like those PO's are setting traps for us.

Similar to what you did, I used a grind stone in my drill press and made up a shim for the tach drive. I also made up a new screw to hold the sleeve in place, as the original was damaged beyond use. My shim worked out to OD=.482" ID=.327" Thickness=.044". This allows for about .015" of axial end play, for expansion etc. I also put a few grooves in the shim to allow oil to get down around the shaft.

jpowell · Posted: January 15, 2009, 12:17 am Post subject: Re: Top End Rebuild

RG, just thought I'd ask how the build is going? I just put the head top back on today, and am anxiously awaiting tomorrow to toque it down. I put new rings, cam chain, and chain guide. So I figured I should see where you're at. JP

Retiredgentleman · Posted: January 15, 2009, 3:28 am Post subject: Re: Top End Rebuild

jpowell;
Sounds like you're making good progress.

I've been cleaning up gasket surfaces and started to polish the engine side cases. Took my clutch apart to check on wear, and found that plates and springs were in good condition. Next jobs, replace the starter motor/crankcase oil seal and set the rings end gap in the cylinders.

My replacements will be; rings, valve stem seals, cam chain, front chain guide, long push rod, and Pamco ignition.

Still more than 3 months of winter Shocked

, so I can just take my time.

jpowell · Posted: January 15, 2009, 10:10 am Post subject: Re: Top End Rebuild

Careful what you say about 3 months left of winter. My bike finally died on me maybe around early oct, and I just parked it thinking I wouldnt have any more riding days till may. Come Thanksgiving it was about 70 and everyone that owned a bike was on it. But me.
Turned out I burnt a valve. Stole some out of a parts motor I got to get the best 4 of the 8. Had to lap the hell out of the one that was burnt, but it's now good. Found the plastic to the chain gaurd in three pieces... inside the motor. The cam chain was stretched so bad that it wouldnt tighten enough, the tensioner would slap each time the cam got tight and back. Took me forever to find that loud obnoxious noise.

Other than that, everything was pretty good. Honed the cylenders, the replacement rings were perfectly gapped out of the box. took FOREVER to route the new chain. Now I know to use the old one to pull the new one through. Then took the chain back off after having it on the cam (togheter, just not crimped) because I realized I forgot to put the chain guide in. (It's my girlfriends fault. Somehow I talked her into coming out to the garage and helping me. I told her to not let me put the head on without that guide in first)

Anyhow, I'm a few days away from being able to start her. Then I'll be pissed I can ride. It's supposed to hit a whopping 40 next sat. Maybe I'll bundle up and see how warm my helmet can keep me.

Cheers. JP

Retiredgentleman · Posted: January 15, 2009, 2:04 pm Post subject: Re: Top End Rebuild

Yeah, girls in the garage will cause distractions for sure; not counting Barb............she's one of the guys Smile

. These 78 Specials need to be out on the open road, not stuck in the garage. Don't forget to re-check your torque settings on the head.

xsjohn · Posted: January 15, 2009, 2:23 pm Post subject: Re: Top End Rebuild

Girsl cause distractions everwhere..........thank god........what ever are the gays thinking...........job openings at Hooters..... Laughing

xsjohn

jpowell · Posted: January 15, 2009, 5:48 pm Post subject: Re: Top End Rebuild

Lol well... She was helpful. I don't know that I would have gotten the chain routed around the crank on the gear without her. BUT. while I was trying to look down int he block, and pull the chain up with a coat hanger, she kept putting her head over top trying to watch. THEN I realized I could take the sump plate off and drop it through. But I still was happy she was there. and even got grease on her fingers...

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

...... and she'll probably never let you forget that one.

And as far as Barb goes, even though we've never met, I think I'm in love. She's got it all going for her - a female 650 owner with now more than one ..... and she can actually put her thoughts down on paper (on line) using the Queen's English !!!!!! (Right xs1961 & Jake68 ?). I don't know .... but the older I get, the more I appreciate the little things in life - like proper grammar and spelling - thanks Barb !

Retiredgentleman · Posted: January 16, 2009, 8:42 pm Post subject: Re: Top End Rebuild

As part of my ongoing rebuild, I was thinking about replacing the shifter shaft oil seal. My question is, can I replace it with the shift shaft in place, or do I need to remove the shaft, which would mean pulling the clutch as well. Looks like I can do it with the shaft in place, just trying to save work.

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