Is my (DR) kit F'd??

Phadam H /
phadam
Jun 21, 2012 11:11AM

I soft seized the DR kit on my Hobbit a few weeks back. It was a real hot day and on one hill I went WOT, ripped down the hill at mach 3, then as soon as I let off the gas... rear wheel lock up! I let it cool down for a bit, and she kicked right over again. I rode it home, all systems seemed okay once I got her up to speed, but there was a complete loss of power off the line along with a faint pinging/clinking sound.

I opened her up and was expecting a ton of blow by... there didn't seem to be too much but there is definitely markings on the piston and the cylinder (see attached pics)

So, is my kit F'd or can I just replace either just the rings, or both the piston and the rings. Do I need to get the cylinder re-honed(?) or should I just buy a whole new kit?

Thanks

IMG_0419.jpg
IMG_0424.jpg
IMG_0422.JPG
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Re: Is my (DR) kit F'd??

Noped Steve /
huckersteve
Jun 21, 2012 11:16AM

Looks like you left some piston cheese on that exhaust port eh? Smarter people will surely chime in here, but I'd think you could clean that up just fine and throw a new piston in there and see how it goes! Whats the worst that can happen, it fails again?

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Re: Is my (DR) kit F'd??

cj cj /
waltz
Jun 21, 2012 11:22AM

You're probably fine. Clean up the cylinder and piston with some fine sandpaper and keep rocking.

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Re: Is my (DR) kit F'd??

JBOT Admin /
capturedbyrobots
Jun 21, 2012 12:36PM

Dr's can take a lot of soft seizing.

I SS my dr when I first got it (being an idiot) and with some cleanup it is a lil clicky but runs awesome.

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Re: Is my (DR) kit F'd??

Phadam H /
phadam
Jun 21, 2012 01:12PM

so new rings (~$18) and a quick freshen up with fine sand paper and I should be fine?? or should I just buy a whole new piston ($55) to be sure?

On another note... There was quite a bit of carbon build-up on the piston head. It got me thinking, am I running too hot of a plug with the kit? I am currently running a NGK BPR6HS. What are you guys running? might a cooler plug help?

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Re: Is my (DR) kit F'd??

Overpriced Parts /
roffman
Jun 21, 2012 01:20PM

New piston

8# plug

Retard timing

Run a head temp gauge Keep below 400 degrees .

Treat your new piston/rings like a new kit and break it in

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Re: Is my (DR) kit F'd??

JBOT Admin /
capturedbyrobots
Jun 21, 2012 02:12PM

I just looked at your pics and it looks like you'll be ok with that piston if you clean it up well. That's what mine looked like after ss and after cleaning up it runs great....just a little more noise out of the cyl.

A new piston would be great, but if you're concerned about another SS just run this for awhile til you are sure your tuning is in order.

No point in wasting another piston yet...

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Re: Is my (DR) kit F'd??

*.* HONDA /
kozanatos
Jun 21, 2012 03:54PM

my dr kit I bought for $30, and it looked like yours, well not as bad.

Friend showed me how to clean it up.

I used muriatic acid to melt the aluminum out of the cylinder. Then I used drywall sandpaper and scratched a crosshatch in and smoothed/chamfered out the exhaust port edge so it wouldn't catch by accident.

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Re: Is my (DR) kit F'd??

Mane Layer /
kallaman
Jun 21, 2012 06:53PM

clean it up and do the drop thru test. bet you'll be fine.

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Re: Is my (DR) kit F'd??

Eric P /
neutral4x4
Jun 21, 2012 09:26PM

Use a little bit of the works toilet bowl cleaner on a q-tip. Wipe it on the cylinder wall and watch it foam. It'll dissolve the aluminum off the cast iron bore. You might need a few applications.

I would keep running the same piston. These are mopeds. They have horrible tolerances anyway.

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Re: Is my (DR) kit F'd??

*.* HONDA /
kozanatos
Jun 22, 2012 12:49AM

I founds some works toilet bowl cleaner over at a grocery store near me. Then i was also at menards or something and i was like ' oah hey, there is muriatic acid.

The works toilet bowl cleaner is only a percentage of acid, where if you have just the acid, it will take like a second to clean up the cylinder. the toilet bowl cleaner takes a while and it can eat up your washbins. Juss sayin` I didn't use it on a q tip, i just squirted it all up in its business. dont breath too much of the fumes coming off of it though. rub it all around.

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Re: Is my (DR) kit F'd??

Bryan Colliver /
thefishstop
Jun 22, 2012 06:50PM

clean it up and run it fix the air leak

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Re: Is my (DR) kit F'd??

Mike Lyions /
mjl
Jun 23, 2012 02:38AM

https://www.mopedarmy.com/forums/file.php/7/88574/IMG_0424.jpg

It doesn't look like you chamfered your ports in this picture. I would definately do that before reassembly even if that wasnt the cause of your sieze. Then a good cylinder honing.

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Re: Is my (DR) kit F'd??

Tracy Meade /
tracy
Jun 23, 2012 02:55AM

Sandpaper and off to the races.

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