Something wrong with bike. Advice please

**blossomsowner** · 2nd May 2008, 20:53

recently bought a 98 rf900r and am very happy with it. However am now having problems with it not running properly. Symptoms are lumpy idle, missing at low revs, almost feels like its running out of gas with a surging feeling. Still surges at highway speeds.....just enough to be annoying especially around corners as i can't tell when the power will come on properly. Once revs get up top end its all go as per normal.

The bike recently got covered with very fine ceramic dust being parked in wrong place. Problem started first time out afterwards.
My first stop was to find and blow out air filter element....put back and problem seemed fine,.........for about five minutes then back again.

so i have replaced filter element and sponge and mesh filter bits as well as they were all knackered anyway. Thought this would fix it but still the same.....
what do you think????????? carburettor jet/s partially blocked maybe, or some other unrelated thing like sparkplugs or something. Just thought i would get some ideas before i start taking the bike to bits again..

**98tls** · 2nd May 2008, 21:01

If mine i would drain gas tank remove carbs and clean put back together.If not a fuel problem then next stop is electrics starting at plugs/leads and go from there.Easier to start the other way round i guess but methinks its a fuel issue,good luck and let us know what it was.

**riffer** · 2nd May 2008, 21:13

I reckon it's blocked jets.

Are you any good at cleaning out carbies? Probably best to spray with a carb cleaner rather than try to blow them out with an air compressor as jets don't really like that.

A tip when getting the carbs back on - they're a right bitch how tightly they go back on to the rubbers - I use a block of wood covered in a towel - lay it flat across the back of the carbs and give it a bit of a whack with a rubber mallet and they pop back on. The airbox is a bitch to get right too.

**YellowDog** · 2nd May 2008, 21:21

Did it run well before the ceramic dust incident?

**riffer** · 2nd May 2008, 21:26

Originally Posted by YellowDog

Did it run well before the ceramic dust incident?

Originally Posted by blossomsowner

The bike recently got covered with very fine ceramic dust being parked in wrong place. Problem started first time out afterwards.

I would say it's likely.

**blossomsowner** · 2nd May 2008, 21:45

ran sweet as before the dust incident........hence my suspicion that its related to that rather than some other problem arising at same time by sheer coincindence. But still can't rule out other problems.......

**YellowDog** · 2nd May 2008, 22:25

You probably need to go deeper than changing the air filter. Ceramic dust is very heavy and it's momentum will take the fine grains into places that are not so obvious to find. The likely hood is that as soon as you started the bike for the first time after the incident, the engine air inlet sucked the crap straight in and there is no way out.

There is never any harm in cleaning out the carb jets. There are some pretty good fuel additives you can get to force out debris from the system.

Will be interested to hear how you get on afterwards.

**blossomsowner** · 3rd May 2008, 09:36

Originally Posted by YellowDog

There is never any harm in cleaning out the carb jets. There are some pretty good fuel additives you can get to force out debris from the system.

Will be interested to hear how you get on afterwards.

thanks for that...........have you used these said additives and do they actually work........or am i better off saving the cash and pulling bike apart again now? Asking this because I have never tried them....

**Katman** · 3rd May 2008, 14:43

If the problem is indeed dust that has got past the air filter and sucked into the carbs it could only be the air jets that would be blocked. No amount of additives in the fuel are going to clean air jets. Compressed air blown back against the normal direction of air flow is the only remedy.

**YellowDog** · 5th May 2008, 07:59

Originally Posted by blossomsowner

thanks for that...........have you used these said additives and do they actually work........or am i better off saving the cash and pulling bike apart again now? Asking this because I have never tried them....

I have seen amazing results from additives. I don't know if it is comparable, but a mate of mine had a bike parked under cover for 2 months at a cement factory. Even though it was under cover, it got caked and took forever to start (2 battery charges and a jump). I don't even know what he bought however the guy at Infinity in Farnborough offered him a $400 strip down or a $40 additive. Not a difficult choice. He had to empy the fuel tank and then add 3 litres of fuel to said additive. The smoke and smell was quite something, but after 10km of riding, he said the bike just started to pull and pull at all rev levels. I have emailed him to ask what the stuff was called, but have not received a reply. He said that one of the other engineers told him not to use the stuff, as the cleaning process would add 10k to the engine wear. He was very happy with the result. Will get back to you when I get an answer.

**YellowDog** · 5th May 2008, 08:02

Originally Posted by Katman

If the problem is indeed dust that has got past the air filter and sucked into the carbs it could only be the air jets that would be blocked. No amount of additives in the fuel are going to clean air jets. Compressed air blown back against the normal direction of air flow is the only remedy.

Katman is of course quite right and you should first look to address any air intake/outlet issues that may be causing this problem. I will still get the name of the additive, as it may be a later option.

**scumdog** · 5th May 2008, 11:22

Originally Posted by Katman

If the problem is indeed dust that has got past the air filter and sucked into the carbs it could only be the air jets that would be blocked. No amount of additives in the fuel are going to clean air jets. Compressed air blown back against the normal direction of air flow is the only remedy.

I'm with him.
If the dust is not soluble no amount of additive is going to dissolve it.

Additives go into your fuel, through your fuel system and through the fuel related parts of your carbs, the dust most likely is in the 'air-only' parts of your carb which the additive would most likely not be in contact with.

Having said that I am surprised that an ingestion of dust has actually caused the problem - maybe it is of a type that cakes solid when it comes into contact with moisture??
Just my 2-cents wirth.

**MSTRS:Me** · 5th May 2008, 12:14

If the dust was fine enough to get through the airfilter, then why would it block anything downstream? It's not as though the air carrying it goes anywhere except straight through the open throats of the carbys, through the inlet manifold/valves and then burnt in the combustion chamber...
OK - it's possible that the carby slides have a coating of the stuff, but that should only make them a bit sticky when opening/closing. If it's on the needles, then it's above the mainjets anyway, so shouldn't be a problem there.
My guess is that if the dust is the problem, then it's causing it at the coils.
Otherwise, the timing of the problem is coincidence and you have the old RF problem of worn needles/emulsion tubes.

**Katman** · 5th May 2008, 19:47

Originally Posted by MSTRS

It's not as though the air carrying it goes anywhere except straight through the open throats of the carbys, through the inlet manifold/valves and then burnt in the combustion chamber...

Ever heard of air jets?