And now the new motor doesn't want to run properly

[High_Voltage]

i got my new ZXR motir in but now when i crank it over theres a bit of a grinding noise when it starts running but it doesnt idle. i have 2 hold the throttle open to keep it going.
could anyone help me with this little problem?

[Hitcher]

Use duct tape to hold the throttle open.

[Slyer]

Did carbs come with it?
Has it got oil in it?

[p.dath]

Where is the grinding noise coming from?

[High_Voltage]

Full of oil and put my old carbies on it off the old motor. they were running perfect before. the noise sounds like somewhere on the right hand side. hard to tell though. well rather than a grind its a real fast ticking noise like somethings either loose or hitting something the cam chain and tensioner look brand new too

[R6_kid]

The C model uses a different setup on the carbs. Pretty sure you'll need C model carbs to make it work. have you tired adjusting the idle?

[Slyer]

Did you read what R6_Kid posted in the other thread?

As far as I'm aware the carbs on the C model are different in that they have a vacuum system, whereas the A model carbs don't.

Can you confirm this?

/edit
Damn you beat me to it!

[High_Voltage]

True how can you tell the difference between the carbs then? I just found out another thing that my cam chain seems to be rubbing on the rocker cover which is weird because its a new chain and tensioner

[Slyer]

Carbs that have a vacuum connect to the tank with two tubes, the vacuum line sucks the petrol down. My bike didn't have the vacuum line attached when I bought it but it still worked because the diaphram on the fuel tap was fucked. :P

[quickbuck]

Carbs that have a vacuum connect to the tank with two tubes, the vacuum line sucks the petrol down. My bike didn't have the vacuum line attached when I bought it but it still worked because the diaphram on the fuel tap was fucked. :P

I think you will find the vacuum line only opens a valve.... It does not suck any fuel down... Gravity and pumps do that task.

[Slyer]

Sorry you are right.

[SS90]

True how can you tell the difference between the carbs then? I just found out another thing that my cam chain seems to be rubbing on the rocker cover which is weird because its a new chain and tensioner

That is actually quite a common fault with the C model ZXR250's.

When you look at the rocker cover, where the chain has witness marks where it has been rubbing on the cover, you need to deftly grind away some of the material there.....a dremel works best.

sure, it's not "the way it is meant to be", but I think the original chains where slightly lower profile than the replacement part.......

This is only on the c model, the A and B don't seem to have this problem.

I have fitted about 20 of the things over the years, and I used to grind them all down when I fitted them, as the first time it happened, the customer was quite annoyed (rightfully so)

Oh, you don't need to run the C carbs, you just need to blank off the vacume hose from the (I think) number 2 manifold.

IF you do for some reason need (want) to run the C carbs you MUST use the C air box, and have all the hoses correctly connected up, the have a complicated air bleed for the vacuum slides (the A and B don't), and if it is not connected up correctly, it will not rev over 8,0000 RPM correctly, as the slides will not come up at the right speed.

The B model carbs will be fine, just remember to blank off the vacuum line from number 2 manifold (I think it is number 2)

[CookMySock]

When you look at the rocker cover, where the chain has witness marks where it has been rubbing on the cover, you need to deftly grind away some of the material there.....a dremel works best.I agree. If you don't have a dremel, an angle grinder with a small disc might fit in there. Be careful you don't go through it. Quite likely you will only need to nick half a mm of material off it.

That is almost certainly going to be your engine noise problem solved.


IF you do for some reason need (want) to run the C carbs you MUST use the C air box, and have all the hoses correctly connected up, the have a complicated air bleed for the vacuum slides (the A and B don't), and if it is not connected up correctly, it will not rev over 8,0000 RPM correctly, as the slides will not come up at the right speed.Yup, and it will probably run really lean somewhere and eff something as well.

Good on you for tackling your own engine jobs. :niceone:

Steve

[quickbuck]

(I think) number 2 manifold.



Im pretty sure you are right... It is usually #2 on must bikes...

[High_Voltage]

True im thinking ive got the c model carbies and had them on an a motor. does anyone have a diagram/photo to show how the carbies hooked up? I just want to make sure i hooked them up right. Im sure i did though

And yea there is some wear on the top of the rocker cover

[SS90]

How about you post a clear picture of your set up, none of this low res cell phone pics though, too hard to see any detail!

[High_Voltage]

Yea can do i just have to get ahold of the Gfs camera 1st because i dont have one except my phone

[crazyhorse]

Hope you get it sorted and can get back out there to ride again soon :)