Hi guys,
Just a question, recently Ive just rebuilt my mc28 engine, is it normal for the right exhaust(bottom cylinder) to smoke more then my left cylinders?, both are consistently giving out smoke, but even after warmed up, the right still smoke way too much, I'm currently on premix, mixing 25ml to per liter.
Any advice is appreciated!

Regards
Jarrod

The short answer is no, there should be a similar amount of smoke comming out of each pipe. There are a couple of possibilities and my first guess was a blown crank seal but first we need more info. When you say you did a rebuild, what exactly did you replace?
Was the bike oil injected before the rebuild?
Have you actually ridden the bike since the rebuild?

mtec666 wrote:The short answer is no, there should be a similar amount of smoke comming out of each pipe. There are a couple of possibilities and my first guess was a blown crank seal but first we need more info. When you say you did a rebuild, what exactly did you replace?
Was the bike oil injected before the rebuild?
Have you actually ridden the bike since the rebuild?

My initial thoughts, I'm with mtec666. Only because I had the same issue last time I started up my MC21.
Have a good crank, so I will replace but you could have the same issue. Right chamber more smoke that the left.

Here's a vid - may help.

https://www.youtube.com/watch?v=4WknRNTvHkw

Ignore the kit, that's gone now.
All Rothmans now.

Cheers
Popes
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Hi guys here's a video of it, let me know if there's anything wrong
https://youtu.be/nskoy_avDyg
Yeah I've replaced all the seals, pistons, cylinders, crankshaft etc, except for one cylinder head the bottom cylinder head which is a used one. Any help will be appreciated 👍🏿

Hi, it's a new crankshaft, nope I haven't put any oils on the crank bearing, yes, that's when I noticed the right side of the exhaust is producing more smoke, both seems to be running fine, should I do a plug check? And does my carb setting makes a difference? Cause both are of the same settings

Hi there
I had this issue once after rebuilding a 21 sp,it was primary side crank seal it was a new seal,I dismantled the motor wondering if I missed the groove in the crankcase that the seal locates in,I hadnt but when I examined the seal closely I could see the seal in the outer flat side
when it was moulded and the moulding tool was pulled away from the seal it left a fairly deep crater across the sealing face of the seal,
i replaced the seal with another new seal with a normal sized dot on the outside of the seal and that cured the problem,It was sucking gear oil passed the indentation in the seal,
If you are running premix there cant be many other reasons for that amount of smoke from just from the lower cylinder,
I hope this helps,
jonmac
_________________
John

Johny macs explanation sounds like a likely posibility. There is a fair chance you may have a dodgy seal. Assuming you are running a non castor premix oil you could try draining all your gearbox oil out and replacing it with two stroke castor oil. When you run the bike you will be able to smell the distinct castor oil smell. That will confirm that you have a leaking Seal.

Hi Guys,

Thanks for the input! will get my crank seal check! will it be a good idea to check the compression as well?

Just for reference (as I'm fairly new to the NSR world) is replacing this seal a job that requires splitting the cases?

What would it mean if the 'LEFT' was bellowing more than the right? 92 SE MC21 Wet clutch model

Looking at a bike and this is happening, so assuming it is not the crank?

Cheers
Popes