Hi guys,

I'm loving my MC28 I restored, but a few weeks ago I overtook a car accelerating to full speed. I overtook a car then shortly after the bike bogged down and only firing on one cylinder. It wasn't seized. I've seized my RGV (Vj23) enough times to know what that sounds like.
So I limped the bike back home for 5 miles on one cylinder and it was really slow.

The plugs are new with the restoration and have done about 200miles.
I took the plugs off and the left(rear)plug was really wet. Sparked when I kicked it and held plug against head
The right plug was quite sooty. Sparked when I kicked it and held plug against head

As I imported the bike direct from Japan I don't know the history but its really fast. Much faster than my VJ23.
The pipes when I first removed them last year for restoration were totally coked up.

With the pipes off I looked up into the barrel and the honing on the barrel looks brand new. Same with the sides of the pistons I could see.
The engine does feel beautiful and tight, and has loads of torque so I'm wondering if the previous owner had a rebore + new pistons and maybe some tuning work.
It's got the standard smartcard and not some fancy HRC one. It'll do 105mph no problem and probably faster.

So does anyone know what size jets are best for the NSR250 MC28?
I get the feeling its jetted really rich
I'm going to try kicking it over with the pipes back on today and a fuel bottle feed.

Am I going to need a plug chop? I've never done one before.

Cheers for any help.

Rich

http://stores.ebay.co.uk/titanclassics
http://titanclassics.com/
https://www.facebook.com/shinybolts
https://twitter.com/titanclassics
https://www.pinterest.com/anim_eddy
https://instagram.com/titan_classics/

Outside of the Members area, the only jetting support is shown on the following page:

http://tech.nsr-world.com/nsr250/all-nsr250/nsr250-stock-carb-settings.php

Your situation is a classic example of why we do not support jetting discussion, as the state of tune is unknown, and anyone stumbling onto this thread via a basic internet search with similar symptoms and little NSR/2-stroke/problem solving knowledge, may blindly copy settings.

I'm past caring what some people think of this policy, as I can't be arsed with being threatened with legal action over it again, so please don't waste your time questioning it.

If you're lucky, it's just a spark plug that's breaking down. Seen plenty of plugs that spark outside of the combustion chamber, that clearly aren't doing their thing once under compression. I've seen BR9ECMs (and R5300As) that just refuse to work properly after getting wet/flooded too.

Personally I would do a compression test on each cylinder. It's very possible to lightly damage a piston and barely mark the nikasil bore. Looking up the exhaust only shows half the story. Maybe pop the carbs off too, and look down the inlets at the other side of each piston. You may even have caught a ring on the corner of a port. Plenty of things you can't see, just by looking up the exhaust, I'm afraid.

I hope it's just something simple, like a plug.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Thanks for that I'll give that stuff a try and I'll check the jet sizes.

Cheers

Rich

Hi Stuntpea
Have you made any progress with your issue?
I would like to add if you can see the rear side of your pistons by removing the carbs and looking down the inlets you will certainly need more than a new plug to resolve the problem,
Come on Andy what time of night did you reply to this ???
All the best,
jonmac
_________________
John

Been staring at that for ages now, John, and can't remember quite what I was trying to convey! Even with an "and" strategically placed in the sentence, it's still not making complete sense... even to me! LOL

Maybe one too many previews & edits!
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!