Only firing on one!

**Mon Oct 04, 2004 9:42 am » Post: #1 » Download Post**

Morning!

Recently got myself an MC21, but when I fire it up when cold, it only fires on the front cylinder, not the top one. Then after about 3 or 4 mins once its warmed up a little, it starts to fire on it then runs ok!

Anyone got any idea's why this might be happening? Putting the choke on doesn't seem to have any effect either!

Cheers Question

**Mon Oct 04, 2004 2:09 pm » Post: #2 » Download Post**

Hey Barry

It might be a bad spark plug for the top cylinder.
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/\/SR-150 SP Its Special

**Mon Oct 04, 2004 3:16 pm » Post: #3 » Download Post**

Hi mate,

Got new plugs in both cylinders. Suppose it could be a dodgy one! Will swap them over and check if the problem moves!

Does the choke only increase the fueling on one of the carbs or both?

**Mon Oct 04, 2004 4:06 pm » Post: #4 » Download Post**

The choke works for both carbs. Check to make sure that the carbs are clean. Also make sure that the carbs are properly syncronized.
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Mike

**Tue Oct 05, 2004 8:52 am » Post: #5 » Download Post**

Cleaned out both carbs, have set the float heights. When you say properly syncronised, do you mean the slide heights?

**Tue Oct 05, 2004 9:31 am » Post: #6 » Download Post**

check that the slides are both at rest at the bottom of the carb. and then open the throtle and check the slides lift at the same time. and rise together. if not adjust the screw that is in the centre of the linkage between the two carbs.
also have you checked the compressions. they should be close to the same on both pots. if the cylinder that is slow to fire up is a lot lower, i would pull the top off and have a look.

**Tue Oct 05, 2004 9:50 am » Post: #7 » Download Post**

Cheers Jeff, I need to find the adaptor for that size plug for my compression tester. The odd thing is that it runs fine once the engine is warm!

I'll check the slide heights tonight, and swap over the plugs to see if Ive been sold a duff plug.

**Tue Oct 05, 2004 12:34 pm » Post: #8 » Download Post**

DONT PANIC but i had a similar problem, i had terrible starting problems and the bike would only run on one until it was warm.......anyway it ended up being my crank, got hold of some bearings (not koyo) and 22 trackdays and loads of sunny sundays and its still going strong. Very Happy

**Tue Oct 05, 2004 1:06 pm » Post: #9 » Download Post**

The bike fires up straight away, even pushing the kick starter by hand, it does seem to fire on the top cylinder, but very intermittantly until warm.

To be honest I cant see how a crank bearing is going to stop it firing on one cylinder, then again, I'm more at home (dare I say it) with a 4-stroke engine!

Thanks guys for all the pointers, I'll give them all a try. Any more idea's though, keep em comming!

Very Happy

**Tue Oct 05, 2004 7:45 pm » Post: #10 » Download Post**

ad not start the bike up anymore m8 untill u do a full inspection
I had the prob same prob on mine only firing up on top cylinder ok it was sluggest firing up
turns out broken piston burnt clutch and crank bearings were shagged on the lsft hand side
hope u get sorted m8
mine's gonna be off the road for a good while

**Wed Oct 06, 2004 8:46 am » Post: #11 » Download Post**

Ouch!

But as I say, its absolutly fine when its warm, say after 2 or 3 mins.

Hopefully I'll get some time on it at the weekend for a thorough look over.

**Wed Oct 06, 2004 9:31 am » Post: #12 » Download Post**

A compression check is number one on the list, then inspect all the airbox fittings, clean the air filter and make sure any breathers are clear.

Check the jet sizes, synchronise the carbs and adjust the air screws.

There is a whole thread on the Forum about a similar problem. Try the search feature for more info.

Andy.
NSR-WORLD.COM

**Wed Oct 06, 2004 9:59 am » Post: #13 » Download Post**

Cheers Andy, jets are standard, I made a note of checking when I cleaned the carbs out. I'll check for air leaks also, but I'm positive I put them back on correctly, I made a point of taking my time to do that.

Got a good list of things to check, thanks loads guys, any other thoughts etc... please post... Very Happy

**Wed Oct 06, 2004 10:05 am » Post: #14 » Download Post**

Andy wrote:
There is a whole thread on the Forum about a similar problem. Try the search feature for more info.

Andy.
NSR-WORLD.COM

Cant find anything! Sad

**Wed Oct 06, 2004 10:31 am » Post: #15 » Download Post**

Hmmm...

Maybe it was on the "old" forum. I have to admit, I didn't do the search first myself!!

Anyway, get a compression test done first. If it seems in order, then make sure the carbs are balanced and the air screws set correctly - it can make a huge difference.

Also, make sure the battery is 101%! If it's not, it can cause all manner of problems on the NSR.

Andy.
NSR-WORLD.COM