Drive gear / clutch drum question

Marshall Mauney · Posted: Sat Aug 17, 2002 9:08 am Post subject: Drive gear / clutch drum question

How much lateral play should there be on the clutch drum and drive gear? Mine appears to have about 20-30 thousandths, but the retaining nut is torqued to TIGHT (or maybe loctited)! I've never changed drive gears on this engine, so this is the first time I've really checked it. How snug should it be?

TIA,
Marshall Mauney

erik nystuen · Joined: 06 Mar 2002 Posts: 319

Marshal,
The retaining nut should be locktighted as there isn't a lock washer or mechanism to assure it doesn't come loose. (That would be a BAD thing).

However this nut is not the one that holds the gear to the clutch Drum. See page 28 of the Rotax Maint manual for Diagram.
The diagram is not that great but if you remove the Clutch drum you will find that the drive gear is attached with a large nut on the inside, there is also a small hole in the drum and a corresponding one on the inside of the gear flange. In this hole is where a small needle pin is located. This in essence locks the clutch drum to the drive gear and prevents spinning of the gear on the drum.
This little needle may be missing or damaged on your engine hence the play in the gear vs. drum.
Disassemble and take a look, reassemble per page 28 and pg 51. Good time to lube the bearing too.

I have used a small air gun (75lbs torque) to remove mine, works great and no need for the piston stop (that seemed dangerous on internals) you can run an air gun off a small Nitrogen bottle at the track too.

Hope this answered your question.

Rotax Max Manuals

Cooper Cook

Marshall, I think your talking about "end Play" for the clutch drum, I have been unable to find a spec. for this ,my play seems about 20-30 thousand. hopefully someone will have an answer!! Chris

Bill Wright

Hi guys,

Welcome to the wonderful world of Rotax. If you will check your owners manual you will determine that the only spec you need to concern yourself with on the clutch drum is the torque you load the retaining nut with. Remember, this is a user friendly, low maintainance engine, built in such a way that you don't have to concern yourself with things like end clearance on the clutch drum. As long as you are using the correct parts ( drum, driver gear, thrust washer and retaining nut ), just put the parts on the crank end, torque to the correct value, and you are done.

I know it's hard to believe, but this ain't no Yamaha or HPV with a clutch you have to 1. lap to fit 2. measure for clearance. 3. remove and reshim with ( hopefully ) the right thickness shim 4. measure for clearance. 5. rebuild and start over every couple of races ( if you're lucky! )

Just accept that the owners manual is sufficient, and that it really is that easy.

Since you've got some extra time, you might see if your buddy with the Yamaha needs some help rebuilding his engine and clutch for his next race.

Enjoy.

Bill Wright
"Get on Course!" with FK www.formulakart.com

Nick Weil · Posted: Sat Aug 17, 2002 6:45 pm Post subject: Drive gear / clutch drum question

A slight bit of play from side to side horizontally is acceptable Marshall. But if your drum and gear wobble or have any vertical play, it's probably time to change your needle bearing. I have seen this happen on only two karts since early 2001...

Nick

Marshall Mauney

[QUOTE]Originally posted by erik nystuen:
[QB]This little needle may be missing or damaged on your engine hence the play in the gear vs. drum.
Disassemble and take a look, reassemble per page 28 and pg 51. Good time to lube the bearing too.
[QUOTE]

I think I didn't phrase my question quite right....the drive gear is still tight with the drum, but the pair of them are moving back and forth on the drive shaft enough to make me wonder whether somethings wrong, or if it's designed to have some play to 'self-align' with the driven sprocket....

MM

Marshall Mauney · Posted: Mon Aug 19, 2002 7:24 pm Post subject: Drive gear / clutch drum question

Thanks for the help, guys! As it turns out, my drive gear and washers were wearing, allowing a bit more play than was proper. A new drive gear combined with flipping the washers over solved it. This all got done in time for a really cool race on Sunday....

MM

Rod Landers · Posted: Mon Aug 19, 2002 7:57 pm Post subject: Drive gear / clutch drum question

...and remember:
11t gets the bushing,
but 12,13 and 14t get the needle bearing.

Mike Robertson · Posted: Mon Aug 19, 2002 8:12 pm Post subject: Drive gear / clutch drum question

How can I tell when the bushing is wearing?

I have a little play also.

Chuck Groat · Joined: 04 Apr 2002 Posts: 60 Location: Salt Lake City, UT

Mike, since the bushing is plastic and only costs approx $3.00, I replace after every three races, but regrease after each race. Takes approx 20-25 minutes to complete the entire project. Its better to be safe than sorry!!