Hey gents just a quick quiz

Got my mc21 fired up for 2nd time in say 3 years, had it running 2 monthes ago ran a little rough but was ok.

Fired it up today, and as the bike warms up and the choke revs drop off it appears that the rear cylinder stops receiving fuel. A gentle rev see's smoke blow from the front cylinder pipe but nothing from the rear cyclinder pipe. The heat disappears from the exhaust also.

Looks like i'm going to have to pull the carbs and give them a good clean out, but as I've not disasembled the carbs on this bike before can anyone tell me what parts i might need to 'overhaul'? Ie- do i need any gaskets? Anything i should replace while I'm at it?

Any info would be greatly appreciated!
Lachlan
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

It's quite a straightforward job on the 21. Remove the seat unit and tank, followed by the airbox if you have one. Make sure you get a good mate with the airbox seal screws, using a good Philips driver as they are made of soft blue cheese and can round off very easily...

Once these are out of the way, access to the carbs is easy. You will need to remove most of the connections to take them off, although you can usually leave the throttle and choke assemblys in situ. The thing to try first is to clean up everything in the float bowl, which is at the base of the carb and held in place with 4 screws. Have a PU container ready to catch the fuel contained in them as you turn the carbs upside down. Once you have the bowls off, you will see some brass jets. Have a look at the float bowl and check to see if there is any build up of a residue. The jets can be taken out gently, using an 8mm spanner for the mainjet holder, and a small flat head/slot driver for the main jet and slow jet.

Clean all of the bits using a good carb cleaner and a toothbrush and re-assemble. At this point you can also check the float height, which are the black plastic pieces in the float bowl, 2 per carb. Holding the carb upsidedown, they should rest with 13mm showing from the base of the carb.

If that doesn't help then we can look at other bits.
_________________
NSR300R - Why did i ever have a 250...

Thanks Maxim! Your a gentleman and a scholar. I'll pull them apart now and have a crack at it. Let you know how i go!

Thanks mate!
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

That's very similar to what mine was doing but its an MC18 , a clean solved the fuel problem , and I also noticed that someone had fiddled with the air mixture screw and that helped somewhat also .

Removed the carbs, pulled the bowls. Heres a pic of the RH bowl...

http://w1.bikepics.com/pics/2006/06/13/bikepics-609010-full.jpg

Was absolutely chock-a-block full of shite. The main jet had scum in it, and the needle had a thick white build up. The slow jet was very clogged.

The left hand carb wasn't too bad at all really, a tiny bit gummy, but pretty good.

Anyway, further reading and educating for me leaves a question -should i have cleaned the power jets while i had the carbs off? Or are they generally ok? Looking at the picture, does this amount of crap lead people to completely overhaul?

As for removing the two small oil lines, does this mean I need to bleed the oil pump? I've since started the bike for 30-40 seconds at idle and no oil through yet...


One day i'll get the seat and tank on it hehehe
http://w1.bikepics.com/pics/2006/06/13/bikepics-609012-full.jpg
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

Yuck! I'd clean the PJ's too yeah, since they are tiny and tend to clog first. If they are, a high speed siezure may not be too far away...

As for the oil lines, a properly working bike shouldn't need bleeding, but if it's been stood for some time I'd want to be sure there was oil present before I sparked it up. Saying that, the oil supplied is miniscule, and it's not as if it's pouring out of the pump. As long as there's oil physically present at the pipe, then you should be fine.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks for the info Dave, yeah it was oiling fine before pulling the carbs... Fired it up a couple hours ago, and the lower cylinder was still not firing properly, although I've done no more than an hours work on these spark plugs i might swap them out and hope for a better result. (both plugs quite wet after I ran it)

Sounding familiar Gravedigger???

Heres a side question for everyone, whats the cheapest way out of a makeshift fuel tank that i can use while i'm playing with the bike, as opposed to having to pull the tank every 5 minutes... ? Anyone got any idea's?
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

If you have a garage, just suspend a fuel tank from the ceiling, and run a pipe from there to the carbs. Gravity feed will do the rest, you just need to pre-fill the line with a bit of hot sucking action. Do try not to drink the stuff though, it's REALLY bad for you!

As for the poor running, have you checked the colour of the spark?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks for the info Dave, yeah it was oiling fine before pulling the carbs... Fired it up a couple hours ago, and the lower cylinder was still not firing properly, although I've done no more than an hours work on these spark plugs i might swap them out and hope for a better result. (both plugs quite wet after I ran it)

Sounding familiar Gravedigger???

Sure does but my carbs were no where near as dirty as yours , the plugs and battery made a huge difference .

The spark plugs after i washed them up in carb cleaner are brown coloured. The battery is 2-3 monthes old....

About to pull the carbs again to do the powerjets....

UPDATE:
Pulled the carbs removed the floats and the aluminium screws that you undo to get to the PJ's are hacked (fekked) and cant get them out, this could turn into a mini nightmare.... anyways..

Also, I've now noticed my slow jets are 40's and the bike is apart from pipes, total stock (SP) mechanically. Would the 40's be my poor running issue?
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

Photo might be a little hard to tell, but the powervalve screw is munted! (this is how i found it, not my doing!)

http://w1.bikepics.com/pics/2006/06/15/bikepics-610437-full.jpg

Anyways, anyone had sucess with any particular technique in removing stubborn powervalve screws? So far I've used a dental drill to clean up the slot, and heated it with a soldering iron -to no success.

Once removed, What is the technique for cleaning powervalves? Carby clean through the pv access, and through the pickup pipe? Any brushing?

If I pull the tops off the carbys for general inspection / clean, is the gasket reusable?
Thanks gents!
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

Get some small lock pliers and use them to bite into the screw and turn it out. You'll need a new jet but should work. That one is knackered!
_________________
NSR300R - Why did i ever have a 250...

Another cheap fuel tank is to make a hole in a plastic jug with a soldering iron and put a petrol tap in to this great for when you've had 2 stroke pipes of from pump as you can make a small amount of mix up to get 2 stroke back to the carbs.
_________________
MC21 SP

Thanks for the tip Moggy, I'll give it a go, tried the gravity feed idea, but gravity was against me!

Finally got both powerjets out after much foooking about and guess what -
ONE POWERVALVE WAS A BLANK (-IE: NO HOLE!) no jokes! coundn't believe it so i pulled out the microscope yep Nothing!

Who the fek has played with my bike in the past? Why hasn't it ever blown up?

The saga continue's..... keep you posted
_________________
........."I love the smell of 2-stoke in the morning.......Smells like victory"............

MC21 Pentax SP...... TYGA'D

A blank? I don't understand what you mean...
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball