SR250, get me close to the ton

maloburro

New Member
I found this 1981 stock SR250 last year and updated the cosmetics on the cheap. Now I’d like a little more power. I started riding it to work which is 13 miles with hills on 55-65 roads.

I know a lot of you on here have modded these. I’m just wondering if anyone knows of a basic header swap. I’ll probably just drill out some holes in the air box for breathing. Otherwise a bigger front or smaller rear sprocket.

If anyone has any experience with these please comment.

Thanks

Ryan

I
IMG_5038.JPG



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maloburro

New Member
Thanks Wrench. Yes he is awesome, I have seen his stuff and may need a few of his bits. I was hoping to find some easy swaps and do this on the cheap.

It’s the shipping that kills it but I guess I should suck it up.


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wrench85

New Member
His stuff is well engineered and tested. Makes it easy. You can make a new header, or cut it into pieces and cut out the inner pipe and weld the outside back up. And holes in the air box would help it breath easier. Definitely better than a cheap pod directly on the carb. Constant velocity carbs like having long intake tracks. The smoother the air is the better. Just remember, any little change in intake or exhaust will require tuning the jets. That’s where Jadus high prices come in. He’s done the hardest part for you already.


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maloburro

New Member
You’re right. And I believe in supporting people who specialize in a niche market. Between the shipping and the exchange rate it just kills it but then again, it’s a fun bike with no payment.

Ok. I guess I’ll bite the bullet and look at exhaust and see what he recommends for the carb. I’d also like to do a sprocket change to help with top end.




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pidjones

Over 1,000 Posts
You’re right. And I believe in supporting people who specialize in a niche market. Between the shipping and the exchange rate it just kills it but then again, it’s a fun bike with no payment.

Ok. I guess I’ll bite the bullet and look at exhaust and see what he recommends for the carb. I’d also like to do a sprocket change to help with top end.




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It would help to know your location. Someone might be fairly local or know of nearby sources. Update your profile so it can be seen.
 

porcelanowy

Active Member
Hello brother in arms :)
This 1981-one is mine as I bought it:
OdlIDhE.jpg


And like you I am doing changes on a budget :)
A1hpD0G.jpg


Any changes to intake (and exhaust) and you should tune the carb.
I am working on 3D printed slip-on filter that looks like velocity stack and replaces the airbox (it would be a while till I am done – no time for hobbies now).

p.s. That seat – what is it and was the installing process difficult?
 

maloburro

New Member
Thanks. I’ll update. I’m in sacramento Ca area.

The seat was a cheapie I bought off eBay for $25. The front tab slides under the tank, I drilled into the plastic fairings under the seat and attached the back of the seat that way, and the very back drops right in front of the black tab.

It was much easier than I thought it would be.


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porcelanowy

Active Member
Hello
OK, me again :D
How did you manage to mount that seat so it looks good on your SR250?
Got mine and it seats like this:
J35avWW.jpg


Did you just bolt it down so the seat bends and fills the gap with the frame?
Or did you do something magical? :)
 

JerryAssburger

Been Around the Block
I plan on "cheating" with mine by making the new seat go back only as far as where the shocks join up. (A really short solo). Are you committed to the longer seat? You bike looks excellent so far. (What size rear tire are you running? I'm going to try a 130/90-16)
 

JerryAssburger

Been Around the Block
Also, Maloburro- I too, am attempting this on The Cheap. So far, I'm going to attempt keeping the stock header and running an aftermarket (cheapo) glasspack, and then a VM34-168 34mm clone carb from Ebay, since both my muffler and my airbox are long gone.
From what I have gathered from Jadus' informative thread is that these motors have dirt-bike in their DNA, so they're (tuned/cammed/ported) to make good power 8000 rpm and down. Going after the low hanging fruit (exhaust pipe, carb/air filter/jetting) will improve things for sure, but unless someone gets deep into the breathing of these engines ($$ and surgery), I think that's their limit. I think you can go from a 16T to a 17T countershaft sprocket to drop the RPM at higher speeds.
I will be following your thread with interest, and I'll try to share any info I gain on mine. BEST OF LUCK.
 
Last edited:

maloburro

New Member
Sorry ya’ll. I got sidetracked with life issues.

Porcelanow your bike looks great! Honestly I don’t know how I got it to sit so flush. It just dropped. Right down in. I drilled holes in the plastic toward the back and bolted them to the brackets for the original seat.

It has been a hard year and sadly I was forced to put the bike outside. The last time I tried to start it months ago after sitting it the float stuck open and gas just drained out.

This weekend I decided pull the carb and clean it out. Lots of rust so I need to install a fuel filter but I put it back together and it fires right up again! I also updated the signals on it. Unfortunately they don’t blink now so I have to deal with that.


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maloburro

New Member
And yea Jerry I’m pretty sure that’s the tire I’m running. The bummer is these tires look new but are over 20 years old. I’ve ridden up to 55-60 but I feel like I should get new(er) tubes and tires if I’m going to ride it on higher speed roads so that will be a few more hundred to spend.


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Luugo86

'73 CB350, '78 XS650 Cafe Killer
Hope things get better for you, friend, and hope you can get back to your bike.. it is a great looking little scoot.
 

maloburro

New Member
Thanks guys. Hopefully a couple more months and things will settle down or even out.


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JerryAssburger

Been Around the Block
Maloburro... that bike looks great! And I didn't know DO THE TON had an app to send pix to the forum. That will be much easier than what I've been doing! You taught a man to fish!
 

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