Primary Chain guide/ Damper

Hi all,
Recently bought a 650 Turbo engine for spares,cause I needed the crankcase halves, and this is what I found, the primary chain guide had failed, it was chewed up and the resulting debris restricted the flow of oil through the strainer on the oil pump, which explained why the cam carriers had deep scoring on them as did three of the five main crank bearings, crankshaft amazingly is undamaged, camshafts are repairable, head, is alas, scrap I think.Right now the important bit, when I lifted the engine out of the frame to strip it down to use these crankcases when I lifted the crankshaft I checked the primary chain guide and it was at the point of failiure, the central mounting point on this had broken, leaving the guide supported at the ends only allowing it to flex more, the guide also had cracks all over the surface ,this I shall call a near miss now there are bound to be guys on this forum stripping motors down guys and galscheck the primary chain guide ,its an easy visual and save a lot of frustration later.
Hope this helps

 

OH yea! We know all about the primary chain guide! Had mine fail and the debris jammed my tranny. We even have an emergency primary chain guidectomy on file for handling this. First report I have heard of it clogging the oil pump. Not too surprised at this due to the close clearance of the sump to the crankcase bottom. We truly appreciate the post. There may even be someone here with a turbo cylinder head. Post a request in the swap and sell forum and see what goes.

 

Hmmmm Does that motor have the hydraulic (oil pressure) piston Primary chain guide tensioner? Seems the guides on those long outlive the primary chains. Although I'm wondering if a chain wear issue ate the Guide??
Take the Primary chain out an lay it on a table (flat surface)
IF.. the top of the Primary chain touches the bottom , purely from gravity.. RUN.. the thing out to the trash immediately... it's destroyed, period.
Just another dramatic example of Yamahas "Superb engineering" in action :roll:

 

Had my chain guide do the parts dance all over my transmission as well. Left me in first gear only a mile from the house. Pulled motor, split case, popped in new guide, lost main bearing shell, got new one, buttoned it up, still waiting to install it. This part is a certain failure item on all of our toys at one time or another so make the investment early to prevent the trouble that surely follows when it fractures!

 

Hi all,
Blue Maxim , will be posting pics of the oil pump and the largest piece I found of the giude in the spare engine will also post a pic of the nearmiss around 1800hrs gmt this sat.as for the head I think I've found an engineering firm that can reclaim the head for me I'll post when I know more
Danilo, not hydraulic on this one ,failiure is proberbly age related, as for the chain ,I bin every chain and guide and replace them every time I need to split the crankcases on whatever bike I own at the time regardless of history because its not worth the hassle later on.
Good to talk to you all
catch ya later

 

New to web site, I feel better knowing others have had the same issue with the chain guide. I had to ride ten miles in frist gear. Can any one tell me were is the best place to get replacement parts ???? need new gaskets, bearings, minor stuff as well. Thanks
popsabiker@hotmail.com

 

Hi all,
cant get the pics to upload i'm doin somthing wrong,if your really interested i can attach a zipped file to an e-mail

 

got an extra turbo ya wanna sell :wink:

 

I believe that I have a primary chain issue. Blue maxim helped me earlier this year and I am pretty sure that my "noise is not my cam chain(I replaced it) My bike makes an awful racket upon startup but is fine after a few minutes of warmup.

I have seen NO evidence of debris in my oil. I have been told that this chain will not break. This talk of failure of the guide scares me/

DO I NEED TO REPLACE THIS CHAIN THIS WINTER?

 

Now that I have some practical riding and wrenching experience on a 750; I must say ... when these 750's are started-up from dead-cold ... they sound like a burlap bag full of tin cans bouncing down a flight of stairs.

The scary knock:
I had and exhaust leak that sounded like a spun big-end bearing. I probed the engine cool, warm and hot listening for a knock that was never there. Just an exhaust donut not seated and blowing-by when it felt like it.

The Yahtzee Dice Cup Shake effect:
That irritating ... something's coming apart ... has you valve clearances checkin' ... top-end probin' ... what the firetruck is that, noise ... that never goes away -- wound up being just combustion chamber noise and with a touch of pre-ignition. Started runnin' high-test. Problem solved.

Air Box suction:
After the big clean, sync and ColorTune ... the engine was so on-the-edge that I considered enlarging the airbox intake port and using a 900's rubber inlet boot. Scrubbed the idea after really getting to like the Formula sounding: "Ooh-whaa, whaa, whee" when I crank 'er up.

Try running some high-test if you got noises happening. To see if some funny noises might go away ... it's worth investing the extra buck.

 

Err,
it was'nt my intention to worry anyone,if I have then I apologise, it was just a pointer if your splitting the crankcases for some reason.No pare turbo I only bought the bike because it was still had the turbo attached.As for RickCoMatic's point ,he's right ,do'nt listen too hard for what you think it is ,all the honda's I've ever owned from a G5 to the 900 sounded like the gearboxes were falling apart till you pulled the clutch in

 

Here are the pics i hope??
1st pic is the guide from the engine being rebuilt
2nd pic is the guide from the donor engine
3rd pic is the debris in the oil pump filter from the donor engine

 

That's what we pilots call a catostrophic failure. Most just have some black bits fall off the metal plate. Looks like yours got eaten by the chain a little.

 

Still salvageable to my eye. Pop a new guide in (don't forget to loctite the securing bolt) after you split the case and you'll be back up in about a day.

 

That's the debris that was fouling the shift drum ... or, all that is what you found on the Oil Pump screen?

 

Hi all,
The oil pump and the munched guide were from a donor engine which I dont the know the historyof all I needed from that really was the crankcase halves,which is another story to be told later, if I find anything of interest later I'll post some pics.

 

I wouldn't do it. If my engine was up in miles , above 50K then I would be giving thought to changing the guide. Mine failed at about 60K. The chain almost ever fails. I don't know of one failing myself. Noone can really say the chain can't fail, anything can break. But I don't see the guide breaking the chain. The chain would would eat the guide like it was a snack.
As this incident points out the greatest threat is the clogging of the oil pump. The failing of the guide is mostly due to age and wear, not that the chain is slack and destroying the guide. Replacing the guide also means splitting the cases. A job not to be taken lightly.

 

Hi all,
Rick,the debris was plastered all over the inside of the crankcase halves, over the shift drum and the gears,p.o. must have drained the oil and taken out the oil filter as neither was present when I bought the engine, after I'd stripped out the parts, more came out in the cleaning of the crankcase halves.
Robert, I'm looking at 6 months to finish the engine alone judging by the scarcity of some of the parts over here.Some would say I'm throwing away the money but hey I'm only going to do this one once.
And Bluemaxim's right,the Primary Chain never breaks, but the only way to check the guide is to look at it and I think you could do it with an endoscope if you did'nt want to split the crankcase halves,you could remove the sump or the starter motor and go in from there assuming you could beg, borrow or buy an endoscope??

 

Yeah I"ve heard that one too.
Seems Sno mobiles have similar chains ..they break them, but in fairness they have significantly more power.
The chain does not need to break to cause serious mayhem. witness yr chain guide. Surprisingly, these hi vo chains get really sloppy early on.
One manufacturing techinque the japanese had not yet mastered apparently. Many owners replace them as insurance.. I suspect more should.