Hi all,

I just had a couple of queries about the idle and slow runnning. I have read the carb tuning guide alot. But I wanted to clarify a couple of terms used.

"If the throttle response is very quick, and you can only feel a little pulsing from the exhaust gasses, then the mixture is lean."

"If the throttle response is poor, and heavy pulsing can be felt from the exhaust gasses, the idle circuit is too rich"

What is it saying when its says heavy/little pulsing from exhaust gasses?

"adjust each screw until the maximum engine speed and throttle response is achieved" What does this look like? As in: it will idle at 1250rpm but the engine will sound like its working a little harder/faster? if that makes sense.

Mine idles around 1300rpm and jumps around a little around 100 - 200rpm but the throttle response seems better than with stock SJ's. But the idle seemed to stay at 1300rpm with the stock SJ's but it took longer too settle back to idle.

I rode my MC21 around this time last year for a track day but it seized after 3 laps massive detonationon the front cylinder the top of the piston looked like a dried lake bed. I have my next track day on March 28th at EC. Nervous to say the least. I replaced the crank and the suspect piston. I couldnt find the cause of the seizure/detonation as I went away for 6 months almost straight after it died and didnt know what i was looking for. I installed some egts, canned the oil pump, blocked the PJ's, pulled out the thermostat and got some Tyga pipes but i only have the stock jetting kit to play with. I have done a leak down test and it held 8psi for 10 minutes no dramas. Compressions was around 120 for each cylinder. I'm hoping that with what i have jetted it to it will be richie rich. I am going to be such a pussy for that first session.

Anywho hope my next post is about a succesful track quest.

knoxy_7 wrote:
What is it saying when its says heavy/little pulsing from exhaust gasses?

"adjust each screw until the maximum engine speed and throttle response is achieved" What does this look like?

1) Put your hand over the end of the exhaust pipe and you should be able to feel the pressure pulses as the gasses flow from the engine.

2) Adjust the screw(s) to the point that when you blib the throttle, the engine revs up quickly and sweetly without stuttering or bogging down.

A bad SJ is unlikely to cause a siezure, especially on track when the main and PJ (if fitted) will be providing the fuelling.
_________________
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Hey mate,

Thanks for the clarification info. It was just a bit of fiddling with the AS to get it to that sweet spot. Which as we know is a bit of a pain to access.

A bad SJ is unlikely to cause a siezure, especially on track when the main and PJ (if fitted) will be providing the fuelling.

Oh yeah I realise that I wasnt going to seize it by fiddling with the Sj's. I think i am just nervous in general as last time out was upsetting.

Lets hope for the best this time round.

Cheers

Hey again.

I have completed a track day on my MC21. What a relief that was. After it seized a year ago I thought the worst. But between then and now I worked on it and researched and spent countless hours tinkering and rebuilding and thinking more. When it finally crackled into life after a crank and top end I was pretty ecstatic. Filling the garage with two stroke fumes was as only you guys would know such a big relief I felt high as a kite or was that the fumes, anyway.
That still didnt compare to actually sitting on it in full leathers with my sights set on the straight before turn two (Eastern Creek). It was a nervous first session to say the least and I was pretty gentle as this was also a heat cycle and new front pads. As the day progressed I got more confident in the bike itself and could relax a little more and concentrate on riding the thing hard. Only when I was going full throttle down the straight was I concentrating on the EGTS as thats where I seized last time. I did have quite different EGT readings one being about spot on 1250 or so and the other quite low at 800 farenheit. Thats another thread though. I think I will pull the front cylinder apart to see if everything looks good because I sanded out the scratches with some wet and dry so it will be interesting to see the results. Could be time for a new cylinder I will see what the inspection reveals. Till then though I will just soak up the good feeling you have after working on something and then it actually holding together for the legnth of a full track day.

Anywho thanks for this site and all the time and effort put in by you guys because without it I would have been pretty screwed also Matt@Tyga as he is a constant reliable source of information for me. I attached a photo from the day.

Thanks again.

Excellent news, well done you!