Craiglist/Sprag Clutch Questions (now with pics)

[Dr. Mordo]

I want a Steamer, and I stumbled onto this one.  I'm trying to decide if it is worth the effort.

http://austin.craigslist.org/mcy/521021592.html

According to the owner, this bike makes a 'rhythmic grinding noise' when being cranked (I haven't seen it yet, I plan to look at it Sunday).  From my research here, I think the obvious answer is the Sprag clutch.  

My questions:

1) Is it worth the $800 he said was the least he would take?

2) How involved is it to do the sprag clutch?  I am a former auto mechanic so I'm not scared at all of pulling the engine.  However, how far do you have to disassemble the engine to get to the sprag clutch?  If I do the work, roughly how much will the job cost me?

Thanks!
Travis

[Stretch]

You have to split the case to get at the sprag clutch, but a decent mechanic with a shop manual can handle it.

That's a fantastic price if you're not shy of a good bit of work.

(Cue dramatic music)
That is, assuming it's only the sprag clutch and not something more serious.

[Dr. Mordo]

I've read thru the sprag clutch threads and didn't see a specific diagnosis.  

What I have gathered about SC diagnosis:

grinds when starter is engaged
runs fine when push started

Is there anything else?

I really appreciate the help!

[steammoto]

If  the sprag(starter gear) is on the way out first  the engine will spin unable to catch followed by a very loud clang sound(similar to slamming a hammer against a  thick metal plate). First hand knowledge

I have priced the DIY fix at about $300-350, this includes all the gaskets(starter gear is $240). So, for less than $1500 you could have one fine machine.

But, I believe you have to look hard at the fact it has 70k on the odom. There could be other issues. Get the bike running/test ride, if all else feels good, the owner has any maintenance records and the bike appears cosmetically well kept it may well be worth the investment.

If closer for$800 I would scoop her up for parts and plastic.

Good luck

[Mustang]

If it was closer I would scoff it in a heartbeat . the engine is probably still fine at 70 k but the parts are there and replacement pcs at the dealer are expensive and unobtainable , ie plastics etc , alternators run almost a grand ! igniters are $700 , etc etc
the person selling it could make a lot more money just parting this thing out on ebay !

[Dr. Mordo]

Well, I bought it, got it home, and kind of got it running.  I drained the fuel and replaced it with fresh hi-test.  The dude was a mechanic and had pulled the carb and cleaned it, so it should be ok (he seemed totally on the level).  After a few push start attempts, we figured out that the starter would catch when we got it out of that stripped part of the Sprag.  So we hooked it up to an external battery and cranked it over.  I got it to run while spraying puffs of ether into the air intake, but it wasn't getting any gas from the tank.  Do I need to burp it after disconnecting the fuel line at the tank valve?

Anyway, while it was running it sounded pretty good.  It definitely needs chain, sprockets and tires before it hits the road.  But I'm thinking if I can get it push-startable, I may ride it for a while as is.  Bad idea?

Thanks for the advice!

[Stretch]

Yep, bad idea.  Push-starting will get it running, and once it's running, you'll want to ride it.  Once you ride it, you'll be hooked, and you'll just have to get it fixed right so you can take it touring, ADV'ing, fishing, camping, etc, without having to park on a hill.  Then you'll be living with a lovely farkle collector, just like the rest of us.

Be warned!   :mrgreen:

[Dr. Mordo]

I have a F650, also, so I'll have a bike to ride when I get sick of push starting a fix the the sprag!

[JetdocX]

I used to have one of those.  You should keep it.  DAMHIK! :lol:

[Dr. Mordo]

Ok.  The bike ran tonight for the first time in a couple of years as far as I can tell.  The tag expired on '05.
 
I didn't replace the sprag.  I repaired it.  I know some (or most) will think I'm a bit crazy, and it may be a dumb idea.  We will see.

What a sprag clutch does is it allows the gear to grab in one direction, but not grab in the other.  The way Triumph did this is to use something like 'teeth' (not a great description) that are held in place by a garter spring (basically a metal rubber band).  In my clutch, the starter and idler gears looked brand new.  The only thing wrong was that the teeth no longer grabbed.  When I disassembled the clutch, it was obvious that the garter spring had lost tension, and that the teeth no longer grabbed.

I looked for a replacement garter spring.  Suspiciously, Triumph doesn't sell that particular part of the clutch, while they sell all the other parts.  Hmm.  No one sells garter springs.  I called spring manufacturers and they had no idea what I was talking about.  Finally it hit me that using a spring was a stupid idea in the first place.  If you keep a spring under tension it stretches eventually.  However, it can't be under much tension or the garter spring would just snap.  So I figured I'd try something different - wire.  I bought some 22 gauge wire and triple wrapped it around the sprag.  Then tried to put it back together.  Too tight.  I pressed in the teeth to expand the wire a bit and got the gear inside of it.  Then I twisted the wire to tighten it up and put it all back together.  The Clutch worked exactly as it should.  It grabbed in one direction, but not in the other.

So.  Gambler that I am, I put it back together to see if it would work.  I figured that the only thing it would cost me is labor.  I underestimated a little bit how painful it would be to get the engine back in the bike.  Once it was in, I put the starter and alternator on so I could turn it over before I had installed many of the other parts.  It turned right over.

So I put it all back together and got it running.  It needs tires and possibly a chain, but not too bad for $800.

Will it last?  Will it outlast a stock sprag?  Only time will tell.  Right now, it sounds badass when I fire it up.

EDIT: It occurred to me that I should post the answers to a few questions I had.

#1) The 51t sprag is the later sprag, and I had it in my '96.

#2) AFAIK, machining is only required if you have the early engine with the removable access cover.  This was not me, but I read that somewhere.

#3) Don't pull the clutch.  It isn't necessary.  Just leave it there on the end of the shaft when you pull it out of the engine.

#3) You will need some weird tools.  For my bike: a 36mm socket, a torque wrench (or wrenches) with a range between 6 ft/lbs and upwards of 100 ft/lbs (135 if memory serves), a pry bar, a rubber mallet to bang on stuff.  This would have taken me hours less but for the trips to the auto parts stores.  Wrestling the engine into the bike by yourself is very difficult.  I used rope and two hydraulic jacks; it sucked.

[Stretch]

Don't try to start it with a weak battery, or let it roll backward in gear.  The slightest bit of reverse rotation of the engine is what kills Steamer sprag clutches.

[fano]

[Dr. Mordo]

Stretch: thanks for the tips, I'll do it!

Fano: I didn't take any.  My wife is out if town with the camera.  I could provide some illustrations if necessary, but once you have the clutch in your hands it becomes clearer what I am talking about.

[Stretch]

Garter springs...

Sounds like the spring used in oil seals to hold the sealing lip against the shaft...



A bearing supplier may be able to find you a large oil seal, from which you could rob the garter spring.  Jest a thought.

[Dr. Mordo]

You are exactly right about the spring/seal connection, and that's exactly what I was thinking before the wire idea hit me.  I did go to a local parts store and they didn't have a seal small enough to harvest the spring.  I was planning to go to a bearing and seal shop before I settled on wire.

Apparently radial shaft seals (like the one you posted a pic of) are now the most common application for garter springs.  By 'most common' I mean possibly 'only'.