Kinetic Woodruff key?

A couple of weeks ago I bought a slightly used totally stock 2005 TFR, with low miles, it ran OK but I had to adjust mixture screw almost all the way out to run, it finally got to the point where it would try to start up, but wouldn't run. Right before this point it was really starting to backfire. I took carb off to clean, and it had a 41 main jet so up jetted to a 48, assuming it was way too lean. No air leaks anywhere, nice blue spark, great gas flow, and good compression, I'm at a loss, could it be a sheared woodruff key?

Re: Kinetic Woodruff key?

One thing also that happened was that I had the Moped on the stand revving to about 3/4 throttle and that's when the backfiring was real evident. I bumped the kill switch, and from that point I have been unable to get it to run, even with a shot of premix into the cylinder it will just sputter.

Re: Kinetic Woodruff key?

Any opinions?

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There's a mixture screw on later models? can you post a pic? The pacco that came on my bike only had the idle screw, like most shas and sha copies, but there is a filled hole that looks like it could have been for an idle-mix screw... I've heard of SHAs with idle mix screws, but was not sure if there were vespa style ones or just the larger 14+. Mine came with a 45 jet, which I thought was stock in all of them, but might have been rich for break in or the elevation it was sold at. How does the plug look? wet or dry? light or dark?

Anyway, it would be good to check the timing with a light, but it's unlikely to slip unless someone took the clutch off and pulled the flywheel loose.

Will it fire on starting fluid?


~m (edited)

Re: Kinetic Woodruff key?

Woodruff key doesn't hold the flywheel in place during running. Only aids in alignment during assembly. The taper fit is what actually holds the flywheel.

Re: Kinetic Woodruff key?

I have nice blue spark, have squirted premix into cylinder, and it will pop, and backfire through carb, this is the adjustment screw, it was out 5 full turns when I checked it, when I pulled carb off to check, I saw that main jet was 41, which from what I've read up on this site is too lean for a stock setup. I thought maybe that's why adjustment screw was out 5 turns.

The reason I suggested woodruff key issues, is because, I have fuel spark, and compression, but maybe it sheared and now the timings all screwed up, but this is my first moped, so didn't know if there was anything else I should check.


Re: Kinetic Woodruff key?

Whoa, never seen that screw before. I want one of those carbs to make in to a 14! Is it a 12 or 10?

If it tries to start only when You add premix directly then it sounds like You have a fuel delivery issue, go through the carb again, make sure to clean out the idle 'jet' passage.

If You're getting spark, fuel, and compression, it should start....

You can check the timing with a timing light (You might need somebody to pedal or use a drill), that would save you pulling the engine and flywheel to inspect everything, or maybe even check on the key with a flashlight if you take the clutch and spacer off, never tried shining a light down the crank, but there's a gap so maybe. It should not come loose off the taper and slip/shear the key without a puller or at least a mallet though. I doubt any shock strong enough could be transmitted through the belt, maybe if something jammed in the flywheel fan blades while the engine is running. (edited)

Re: Kinetic Woodruff key?

Actually there's no difference if I spray premix into the cylinder, it just pops and sputters, the same without spraying. I was thinking that if it was a CDI that the timing is what it is, and no way to set it? It's got good spark, and was thinking maybe it's sparking at wrong time, was why it won't start.

Re: Kinetic Woodruff key?

Yeah, the only way for the timing to to change without modification is if the flywheel slips, if you've eliminated everything else it's worth checking out.

Re: Kinetic Woodruff key?

I agree with Macilius. I had this exact same issue on another two stroke, and the crank nut had loosened, screwing the timing completely by shearing the woodruff key. Engine removal is simple...two nuts and three bolts along with airbox and carb and exhaust.

Larry at Cosmo in Pennsylvania has the correct woodruff key if needed. His number is 215-237-0974.

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george boardway /

I had the same thing happen yes it was the key but the mag was shot the hole wablled out larry sold me a new mag a vespa key fits I went to tighten the clutch nut and the crank broke off so I replaced the crank the kinetic mag fly wheel again the slot wobbled out treat got me a pinaso mag flywheel and it fixed it the center hub is steel larry had a late TRF riveted flywheel the center is steel not pot metal that's the one you want if larrys out of business try bill web at zippy moped

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Thanks for the help guys, I have some time off tomorrow, and am going to pull the motor, but can't figure out how to get this clutch housing off, what am I missing? Do I need a special puller for this?


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Never mind, got it with more force than I thought it should take.

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At a loss on how to get this sleeve off. It will not go any farther, and I'm afraid I will destroy it if I put vice pliers on it, I've lubed up the crank with PB Blaster but it's stuck solid. Anyone have a trick or solution to get this off?


Re: Kinetic Woodruff key?

give it a good soak in penetrating lubricant and try a three-jaw puller, or a bearing puller, its probably rusted and party frozen on in there. some heat will help too.

i like how they put the pedals higher on the newer subframes..and plastic fan, and the weird belt guide thingy i've never seen before. keep the pics coming.

actually, can you take a pic of the other side of the sub-frame showing the area around the carb. my original one had holes all over there and cracked, got a later replacement that was a better stamping with fewer holes, wondering about the 2000s models.


~M (edited)

Re: Kinetic Woodruff key?

this part

Re: Kinetic Woodruff key?

Finally got it off, I had to take it to someone who had a puller, and he popped it off. woodruff key was sheared in half. Got it ordered and then will put it back together.

When first looking at the moped I thought it would be more difficult to remove the motor, but it actually was a piece of cake.

Maciek, here's that picture you wanted, and thanks for the advice.


Re: Kinetic Woodruff key?

Glad You found the problem! (and sorry if We led you on a wild goose chase, guess You should have just went with Your hunch and checked that first, but you always want to check the basics first right).

Thanks for the pic too, those later model sub-frames look less swiss-cheezed. I have a later earlier-model one also that does not have the top-most oval hole my old one broke around, it would be nice to have the pedals a bit higher too though, oh, and a pedal-crank shaft diameter that accepts standard arms...

(Scotts late-model subframe linked from above)


Re: Kinetic Woodruff key?

Neil Burgess /

My 2003 looks like that subframe. I've been thinking the woodruff key is same on mine. Runs but backfires and has no power. Maybe I'll finally pull this thing out and see. Haven't had much time, and the 2 hobbits always come first lol

Re: Kinetic Woodruff key?

Got the new key in, and everything buttoned back up, adjusted the fuel mixture and idle just right, and now it runs great, no hesitation, or backfire. With the new jet it now starts with no choke.

Thanks everyone for the suggestions, and advice.

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