Author Topic: Friends 1972 JT60 got er done! (Read 4041 times)

Don R · « **on:** June 15, 2015, 02:35:24 PM »

I'm doing a mechanical restoration on a friends 80cc pitbike. He bought it new in 74 for his wife to ride at the drags. The engine seals are leaking air and it doesn't run. I'll be learning a little on this, I never messed with 2 strokes much.

grcamna2 · « **Reply #1 on:** June 15, 2015, 07:47:50 PM »

I look forward to your resto. project on it

754 · « **Reply #2 on:** June 15, 2015, 08:08:27 PM »

Build it bozuki style...the look on his face will be priceless...

Don R · « **Reply #3 on:** June 16, 2015, 11:08:22 AM »

It's a JT1 mini enduro 60 . I'm just doing the mechanical part, I have 3 chassis items on the way, It's missing a couple small parts here and there and a little beat up like you'd expect a 40 year old pit bike to be. I'm assuming the engine will run after the new seals. I have an article on it somewhere.

Don R · « **Reply #4 on:** June 24, 2015, 03:55:42 PM »

JT60 has no spark, I'm totally a noob when it comes to rotary valve 2 strokes. There are points somewhere, I'll have to find them. I found timing and point measurements. Have yet to determine what they mean.

Don R · « **Reply #5 on:** June 24, 2015, 05:24:26 PM »

I spun it with a battery drill, it's sparking now, I cleaned the points and WD40'd them to remove the water from me washing the turd at the car wash. I gave it a sip of WD in the carb while spinning, nothing yet. It still needs crankcase seals too.

Vinhead1957 · « **Reply #6 on:** June 30, 2015, 12:12:30 PM »

WD stands for water displacement. No telling how many cars I started after the distributer cap got moisture in them with WD

Don R · « **Reply #7 on:** July 05, 2015, 07:10:39 PM »

I've never seen a front sprocket so worn, the cover had so much dried grease/mud behind it, i spent a half hour digging it out with a screwdriver. I didn't want to break the clutch spring. It does pop now when I spin it and Babbits Parts are trickling in the seals and o rings one/two at a time. The shipping was likely more then the seals.

MoMo · « **Reply #8 on:** July 05, 2015, 07:25:20 PM »

Don, if you need a flywheel puller I can loan you one but they are not all that expensive to buy. Have fun with the 60...Larry

Don R · « **Reply #9 on:** July 06, 2015, 06:48:47 PM »

Thanks Larry. I've got buds snap on tool box in the shop, he has most of what I don't. We should be good to go. This is the most beat on little bike I've seen. Even worse than my first cb400F. The present owner was an automotive shop teacher then, an industrial maintainance manager and is a Blown alcohol drag racer. Crazy.

Tonight I got the engine out and removed the compression release, it was rusted and wouldn't move either way without help. Back online to shop for parts tonight.

Stev-o · « **Reply #10 on:** July 06, 2015, 08:23:55 PM »

The crank seals on old 2 strokes tend to leak when not changed over the course of 40 years.
If that's the case, it will not run properly.

Don R · « **Reply #11 on:** July 06, 2015, 08:46:50 PM »

Yep, Stev-o the plan is to seal the case and give it a try. It has compression, the release was sticking so I removed it, tomorrow I'll check with a comp gauge and throw a pair of new plugs plugs in the holes. The rubber carb cover was warped so I got a new one and the spring that holds it on.

Don R · « **Reply #12 on:** July 15, 2015, 07:41:00 PM »

The last seal came today. I ordered 8 items, I got 3 then 2 then 1 then 1 then 1. Five boxes shipped total. In all fairness I bought from babbitts online and didn't set up an account,v that may explain the lack of communication. HA!. It took almost a month but at least I got it.

Don R · « **Reply #13 on:** July 20, 2015, 08:01:16 PM »

I was rattling off the flywheel and it got away from me, it spun and broke the piston skirt. Fudge, except I didn't say fudge. Oh well, it probably needed bored anyway.

MoMo · « **Reply #14 on:** July 20, 2015, 08:46:06 PM »

Quote from: Don R on July 20, 2015, 08:01:16 PM

I was rattling off the flywheel and it got away from me, it spun and broke the piston skirt. Fudge, except I didn't say fudge. Oh well, it probably needed bored anyway.

I 've made many mistakes working on bikes(like somehow setting the DS6 aflame) but have not done that

You're right it most likely needed boring...Larry

Redline it · « **Reply #15 on:** July 31, 2015, 11:17:31 PM »

I picked up a used yz 80 water cooled for $500, over 20 years ago. It wasn't flashy, but it ran pretty well for a long time. Then seized the big end bearing, had one pressed into the crank halves by a "Riders Choice" motorcycle shop, for $75. When I picked it up, there was a deep v type gouge straight across the flywheel side threads, I seen it and thought it might have been some form of "lockwasher effect" that they added, after they were the machine shop. Put it in, it starts on first kick, and kind of vibrates, would never rev on the pipe, ever again. Somebody in the store dropped it, and didn't say a word about it.

Have fun with this one!

Don R · « **Reply #16 on:** August 05, 2015, 10:34:10 AM »

We got a +1 piston and rings. I know an awesome 2 stroke guy. We're going to turn him loose. He bored my 836, the clearances checked out awesome.

Don R · « **Reply #17 on:** August 22, 2015, 06:42:18 PM »

Well the piston isn't the one I supposedly purchased on Ebay, it's .050 over and should have .025 over, it's already bored and now I need a 42.5 mm ring set, all I can find is Stihl saw rings but they are thinner. 1.2mm I measure the stock ones at .058" or 1.473mm.

mrbreeze · « **Reply #18 on:** August 22, 2015, 08:58:40 PM »

The only 2 stroke I've ever owned was a 68' Kawi 120 when I was a kid. I don't know why but it had a thing for breaking the woodruff key that held the flywheel to the crank. Everything always looked and felt tight but it would shear that sucker off every few months. I started buying 3 or 4 at a time. Ended up swapping that bike for a 305 scrambler that was bare bones stripped for dirt riding. If it weren't for my age (58) I'd love to have a 2 stroke again to play with......maybe a 250-500. I know if I put it down I wouldn't get back up as quick as I used to!!

Don R · « **Reply #19 on:** August 24, 2015, 09:18:49 PM »

wiseco had a 42.5mm bore set for a kawi, I need to check the ring thickness in the morning.

Don R · « **Reply #20 on:** September 16, 2015, 07:51:38 PM »

I found rings on ebay, got it put back together and it runs like a scalded dog, I needed to adjust the brakes. Yeow that fence was coming fast! The carb drips if I leave the fuel on, I gave it a dose of VP race gas and I'm going to see if it cleans up before taking it apart. The cb900c leaked like a sieve the first time it had gas this year but now it's good.

Stev-o · « **Reply #21 on:** September 20, 2015, 11:16:05 AM »

Quote from: Don R on September 16, 2015, 07:51:38 PM

... got it put back together and it runs like a scalded dog

Two strokes are fun! I especially like riding the Kaw 500 Triple I recently rebuilt

Don R · « **Reply #22 on:** September 22, 2015, 08:41:25 PM »

I got a ride on a 500 but it had the 750 engine in it. He smoked a guy that secretly had a big bore kit put in his cb750 over the winter. The kawi guy heard there was something afoot and swapped it to the 750 engine.
The same guy totalled out his 900 ltd kaw but a week later was riding (it) again. I always wondered where he got things.
Anyway the 500 frame with the 750 motor was scary fast and what a sound.

Stev-o · « **Reply #23 on:** September 26, 2015, 12:23:58 PM »

Quote from: Don R on September 22, 2015, 08:41:25 PM

I got a ride on a 500 but it had the 750 engine in it. He smoked a guy that secretly had a big bore kit put in his cb750 over the winter. The kawi guy heard there was something afoot and swapped it to the 750 engine.
The same guy totalled out his 900 ltd kaw but a week later was riding (it) again. I always wondered where he got things.
Anyway the 500 frame with the 750 motor was scary fast and what a sound.

Cant imagine riding a 500 frame with a 750 in it?!!

mrbreeze · « **Reply #24 on:** September 26, 2015, 04:29:11 PM »

The only time I rode a Kawi triple was a street legal (barely) 750 in a 500 frame. The owner let me take it around the block. His wife worked at Denco so therefore he knew people in the know and got discounted parts. This thing was sick!!....lightweight, idled like sh!t so you would have to get rolling on it to give her the steam. Once it hit......it was all about HOLD ON TIGHT!!

Don R · « **Reply #25 on:** September 26, 2015, 07:09:56 PM »

This monster gained rpm in every gear, at the top end it was a scary sound. Rider problem maybe.

Don R · « **Reply #26 on:** September 28, 2015, 04:22:26 PM »

I tallied up the bill and it hit $700. including all the broken parts I replaced with ones from Ebay, 2 hours labor for a shop to put in the seals. Then a piston, rings, $60 for boring porting and chamfering plus $170 for tires tubes sprockets and a chain. And that's no labor for me yet.
I made a kill button from a toggle switch, an Adel clamp and an aluminum tab too.

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Author Topic: Friends 1972 JT60 got er done! (Read 4041 times)