Hi guys, last week I aquired an old MC18 race bike.

It's been sitting in a shed for years, the slicks on it were shot etc. However I've had it up and running with 25:1 premix with TTS Full Syth problem is the bottom cyl only appears to be firing intermittently (well one smokes like a b*stard the other only has wisps that increase with revs, like my other 2stroke)

I see it's an R2J as it's 1988? Anyhow it has PGM not PGM II and the old style MC18 pipes. Do the first MC18's with PGM have issues with missfiring due to dry solder joints in the cdi like the old MC16 (since its not PGM II).

What sort of compression should I expect out of these things with a tester ?

Also what else should I do to the thing, I've lubed up its chain which doesnt appear to have tight spots. It'll have new slicks front and rear, i've dismantled the calipers cleaned up the pots and completely bled the brakes, got new sparkplugs in it. Isn't running a filter in the airbox, but it doesnt look to be modded at all. Fairings are rough old fiberglass that have seen tarmac a bit, so i'll give them a cheapish race paintjob too.

Ok further investigation:

according to this site the MC16 uses completely different setup to my PGM, from the diagrams at least. My bad.

So I discounted that, got the bike started and it was running on one for the first 20seconds. A bit of gentle prompting with the throttle got some smoke out the other one with a few crackles and misses then it started right up.

With both of them running I let it idle, which it did without too much bother for a bit, revved it to ~5k and the first cylinder which was running stopped while the other kept going, then it came back after a wee bit!

Revs out cleanly to around 8k rpm and then bogs quick and stalled out at 9. After that I noticed the specks of oil on the ground that was coming out with the exhaust.


So 25:1 is that too rich, is this thing jetted wrong or more likely to be sucking gearbox oil thru and out, fouling the plugs?

I can't comment on the premix side of things, so I'll leave that for someone who can

Actually it'll be interesting to know what a wet compression reading is compared to a dry compression test. It will give you a rough guide to ring condition too.

The specks of oil on the ground can also be condensation in the chambers, much like how a cold car will dribble until it is warm.

Welcome to the forum, you'll have to show us a few pics of the bike.

It's also good to see that you've found a lot of the technical data, searched and what not

Well engine cold I got ~75psi from each cylinder. I know 2-strokes are supposed to be lower than 4-stroke so is that in the ballpark?

Thanks mate, no pictures of the bike for a bit its a fair wreck. I do have a black/white one my friend took since the fairings are such poor quality and paint.

Edit*
Ooh I see ~110psi up to temp is a good min reading, I think it could probably make that.

my own personal paranoia means that I would do a top end rebuild on it before you do anymore to it.....just so you know where it stands and you'll also get to check out the barrel condition. To me, your readin sounds a bit low, I'd try a wet reading and if that is significantly higher, then you know it is worn rings as one of your problems.

Yeah I think I probably will whip the heads off, but first I have another problem!

It won't run anylonger, no spark I suspect (kinda hard to see and kick on my own!)

Its got a fresh battery, and it always used to cycle the RC valve motor when I turned the switchblock to 'run' now it doesn't and it also doesnt fire up.

However if I turn it off, manually shift the RC motor it will then reset to lo if I turn the switch on (so at least it gets some juice, its got no lights afterall).
Fuses in box are all intact

Either way, no amount of kicking cleaning the plugs or push starts will make it fire again. Last it was running it was going like I said above that quick stall at 9k was the last it ran. Still kicks freely and has compression.


I checked the coils on the lowside of them, with the bike in 'run' they give me 0.6v that sound right or do they get a +12 feed?


I'm not a whizz with electronics unfortunately, and the loom looks awefully daunting going into all the cdi boxes and reg/rec

how new is the battery? If it's the same one that has been sitting in the shed iwth the bike, that could be the culprit.

No its a fresh battery, and I tried my GSXR750 battery on it to no avail either.

I'm just not sure if its meant to be 12v to the coils when its not being kicked over or not. I've got the ignition fault finding pdf open from this website so i'll try and go through it.

My MC18 didn't run properly until the carbs were cleaned & set up properly. It also ran rough before the top end was rebuilt. I was also told the silencer on the l/h (front cylinder) was a bit clogged up.

Hi .
It might be worth a look at the two pick ups on the flywheel ,I had frayed cables that shorted out on the flywheel which shut the PGM down .Next day it would run again for a bit ,have a good look and take them out. The servo doen't move on the 18 unless it is in the wrong position , so yours sounds ok . Good luck.

Thanks for the suggestions guys, the flywheel is exposed since its a racebike and was quite rusty. It's been cleaned up a fair bit, the pickups look good but I might take them off and inspect closer.

A picture, black and white and hard to see anything on - by a friend its quite a bit rougher than its made out in b/w fairings are spraypainted repaired a few times in places etc



Not sure how cheap/expensive 2T 250's are over there, but in NZ they go for silly money if they're road legal. However this thing cost me bout 220pounds so i'm not really too fussed

Still not sure on the electrics, was busy in the weekend.

I did however pull the carbs and give them a clean, but alas they were surprisingly clean already. Original owner probably drained them before storage.


I did notice what appeared to be/smell a small amount of petrol/oil in the radiator. So I'm guessing i'll be whipping the heads off at some point in the near future.

Will try spark test and electrics too though. Coolant level hadn't changed, and I dumped the fresh transmission oil to double check and it wasnt contaminated.

Well I went back to it tonight, tried for a bit and got nothing.

unplugged all the connectors for the reg/rec cdi's and a few extra bullet connectors. Stuck them all back in, wound up the idle screw kicked it and way hey started first kick straight up to a cracking 6k rpm din.

Wound down the idle, and it was going as nice as ever although the right pipe (when sitting on it) wasn't really smoking much at all (just pumping air more or less) just like before.

Tried choke off and noticed the cable had come out of the lever, put it back in turned it off and it started to die revved it a bit manually with the throttle and it just petered out.


Had some issues getting it going again, but I think i'm closer to sorting it. I dumped the coolant ... brown mucky water (not the clean i put in) and a thin oil film on top, reeks of fuel...


so no more running it methinks, until i've pulled the barrels inspected and probably purchased a new top end kit for each piston. Sound like a good plan?

Also checking the jetting (I know specifics arent allowed to be discussed here??)

I found (sitting on bike again)

Left carb

MJ = 125
AJ = 38

Right carb

MJ = 120
AJ = 38


why is one jet larger than the other, because of cylinder airflow/temps? I'd ask for recommendation on open filters/premix jets but if it's a no goer thats fine I can ask my local 2T tuner.