Urgent help needed, could have found the problem

**kneescraper** · 9th April 2007, 13:51

Hey all,

Well my new RF400 has been running rich, using 17ltrs of fuel every 130kms, now me being the kinda guy I am I had to find out the problem.

What I have found after stripping the tank, fairings etc off my motorcycle was a cover/bung thing missing for one of the carbs. When the motorcycle is running this makes a wish wish sound...when I put my thumb over it I can feel a strong vacuum. I'm guessing this is little port is for carb balancing...this would make it run lean more than anything wouldnt it?

The bung would have been knocked off when NM was refitting the carbs or when they were rebuilt. Should I cover the port? The noise is quite loud and thats what made me look there.

Cheers in advance.

**Kickaha** · 9th April 2007, 13:56

Originally Posted by kneescraper

Should I cover the port?

yes, I would think it would lean it out on that cylinder

**Squiggles** · 9th April 2007, 13:59

thats the bit used for carb balancing, on my gsxr they're all covered cept one which attaches to the fuel petcock, acts to suck the petrol into the fuel lines... not really sure what effect it would have on the running of the bike though

**kneescraper** · 9th April 2007, 14:04

Oh ok, well that makes the mind boggle alittle more. There is no pipe around it and the bike has a electric fuel pump. Also the air filter has been oiled up big time...its really sticky...like really. Is there a easy way to clean that stuff off....not all of it of course.

**kneescraper** · 9th April 2007, 14:17

Ok...well I have covered the hole up and sealed it, tried to wash the filter with strong hand cleaner and that did nothing...ideas ?

**surfer** · 9th April 2007, 14:17

Hello there, not too sure of your bike and the set up but sounds to me like a vacumn hose that has been closed up so that your carbs run on gravity rather than sucking the petrol through. If this is the case then one carb would be running lean not rich.

If there is a bung on the other carb then it might be worth putting a bung on this one. (I made one for my carb from a piece of fuel line with a chopped off golf tee stuck in one end and clamped tight). Before you do this, does the bike sound like it is running ok, not back firing or anything like that? Backfiring and not being able to idle properly indicates that it is lean.

However, 17liters for 130km is only about 7km/litre. Man that is a serious problem. You should get at least three times this amount.

In which case is there a line (vacumn line) that comes from your tank and goes no where, not the breather hose? Could be the vacumn hose has fallen off altogther, is there a hole in the tank? Have you started to ride like a hoon and burn up more gas than normal? Have you put a new fairing on recently that could add kms to the litre? Is fuel coming out through the hole in the carb, in which case you would probably smell the petrol?

Maybe others could add some ideas also, but that is where I would start.

**kneescraper** · 9th April 2007, 14:26

Cheers, great feedback.

The bike, when standing still does have a faint smell of fuel...however not over whelming. Nope, not hooning....riding normal really. Fairings? stock standard as far as I know. Not sure if the fuel is coming out that hole..no stains or marks to show it. I will have a hunt around the bike to see if there is a hose to connect to that hole.

The bike has always run well, not spitting or farting. With the hole covered up it runs just as good but with out the sucking sound. However the bike does blow a little black smoke when revving (in the past, im yet to see black smoke with the hole bunged up), this is a indercation of running rich isnt it. Also the fact that it uses 17ltrs is another indercation.

Cheers.

**kneescraper** · 9th April 2007, 14:48

I searched and searched and searched but there doesnt seem to be any pipe that connects to that hole. Mind you I did find the fuel light sensor was discconnected

.

Any way I Have put the tank back on and connected eveything up, It blows alittle more black smoke than before...must be cyclinder 1 is running alittle richer now that the hole is covered up. I also cleaned or should I say tried to clean alot of the air filter sticky stuff off...thinking it should allow more air flow...how ever this didnt change much. The only thing I can think of is after the carbs were rebuilt the fuel mixture screw was set to rich...and I need to lean it out...but with the lack of RF400 info out there Im finding it hard to get any information.

Any help would be great.

**Ixion** · 9th April 2007, 14:50

So what do your plug readings look like ?

**kneescraper** · 9th April 2007, 14:56

Aye? Come again? Spark plugs?

**kneescraper** · 9th April 2007, 15:06

The sparkplug is covered in black soot....stinks too hehehe The electrode? is also black...very black.

**Kickaha** · 9th April 2007, 15:07

Originally Posted by kneescraper

The sparkplug is covered in black soot....stinks too hehehe The electrode? is also black...very black.

just on that one cylinder? have you checked them all?

**kneescraper** · 9th April 2007, 15:09

I havent checked them all. Im running out of sunlight and dont have the time to check all of them...this spark plug is from cyclinder 4 not 1, which had that cover missing on the carb.

**Ixion** · 9th April 2007, 15:10

Yep . Black electrode is either burning much oil or running rich.

But wasn't this Mr Nudemetalz's bike? And didn't he get it all sorted?

I'd look with enormous suspicion at that aircleaner. It should NOT be sticky. Oily yes, not sticky. Can you temporarily remove the aircleaner.

**Kickaha** · 9th April 2007, 15:11

Originally Posted by kneescraper

I havent checked them all. Im running out of sunlight and dont have the time to check all of them...this spark plug is from cyclinder 4 not 1, which had that cover missing on the carb.

you need to check all four, what you have described would indicate it is running rich, but you need to check and see if it doing it on all cylinders