2 Stroke Jr 80 carb upgrade???

J

Jayj72

Hey guys new to the forum
I'm really having trouble figuring out a new carb for my JR 80 it's completely stock nothing changed I believe its a mikuni 20mm and I was wondering can I goto a 24mm and also can I goto a flat slide as it has a round slide now any info as far as upgrading would be greatly appreciated I'm also planning on putting an fmf muffler on it and a better airflow filter
Thanks
 
Redordead89

Redordead89

I've sold a few Honda CR carbs to Vespa owners in the past, with a little ingenuity anythings possible! Although the stumbling block would likely be the size of the inlet manifold!
 
bweighmaster

bweighmaster

It's All about your ability to improvise , bigger carb means bigger intake , air filter , maybe changing throttle cable , ..how about the choke ? What size jets ? Can you say , Can of worms ??
 
J

Jayj72

Not sure what size jets it has but I know when I pulled the carb off there's a deep scratch on the throttle cylinder where the slider goes and one of the brass fittings that has a tube hanging is broke so a new carb I think would be best.
I can't afford a new bike and the bike only has maybe 50hrs on it bought it new 2001 JR 80, for my son and used it one summer and it was used a couple times after that and its sat for the past 15 yrs it started but would stall and idle very rough so I've got it torn down and rebuilding.
New rings, new gasket set, spark plug, not touching bottom end as I'm sure it's fine but I'm stumped on what carb to go with, I've heard a flat slide is better than a round slider is this true? I was also thinking of getting one of those carbs off of wish or Ali express for 30 dollars just to test one of the bigger sizes out and if it don't work well its only 30 dollar loss rather than 200.00
 
SRAD97750

SRAD97750

Moderator
Staff member
The DS80 was replaced by the JR80 but the parts remain the same.
I get replacement carburetors from eBay in the $20-30 range for small displacement engines that have cracked/worn/missing carburetors. They are usually 100% right out of the box, besides fuel screw and minute idle adjustments. Be sure to match the part by pictures. If it doesn't look like your carburetor, don't buy it.
I have tried getting larger intake manifolds and carburetors to gain performance, but it typically only gives marginal gains on the top end, and usually have better results with properly jetting the stock carburetor and getting a cone/pod filter in conjunction with less restrictive exhaust.

Good luck! I have had great results with many small bikes.
-BIG DAN:thumb:
RED 027_1.JPG
 
2strokesteve89

2strokesteve89

SRAD97750:
The DS80 was replaced by the JR80 but the parts remain the same.
I get replacement carburetors from eBay in the $20-30 range for small displacement engines that have cracked/worn/missing carburetors. They are usually 100% right out of the box, besides fuel screw and minute idle adjustments. Be sure to match the part by pictures. If it doesn't look like your carburetor, don't buy it.
I have tried getting larger intake manifolds and carburetors to gain performance, but it typically only gives marginal gains on the top end, and usually have better results with properly jetting the stock carburetor and getting a cone/pod filter in conjunction with less restrictive exhaust.

Good luck! I have had great results with many small bikes.
-BIG DAN:thumb:
View attachment 32843
Click to expand...

oof!
 
J

Jayj72

Thanks! That will help out
Do you notice any difference in a round slide carb to a flat slide?
Can you swap one for the other as I'm sure you can tell I'm not to familiar with bikes I grew up around cars, pulling motors building motors so I'm mechanically inclined just not to knowledgeable with bikes
 
bweighmaster

bweighmaster

No difference , slide to slide , the difference is in venturi size .. smaller bore means more intake velocity . Making it easier to suck the gas out of the jets ...
 
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