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View Full Version : 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
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
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
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

kneescraper
9th April 2007, 15:14
I did remove the aircleaner and it still blew smoke, the cleaner is sticky with the oil stuff. I will buy a new filter element tomorrow.

This was NM's old bike, the bikes running fantastic....however its running far to rich...blowing alot of black smoke and from what I have just found out killing the plus.

There is no sign of oil usage...I will change the oil and keep a very close eye on the level...however I will not be able to do this untill tomorrow or Wends.

I would love to get to the bottom of this...I cant afford to run a bike that goes though $50 a week of gas.

kneescraper
9th April 2007, 15:15
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

Well if its gotta be done, its gotta be done. I'll be back in 10 mins to report.

kneescraper
9th April 2007, 15:26
Ok, all spark plugs are black with soot. No oil on the spark blacks just dry soot.

Colapop
9th April 2007, 16:05
There's a spark plug guide (pic) somewhere on here - I'm f*cked if I know where though. It has a pretty good description of the problems spark plugs have.

Disco Dan
9th April 2007, 16:15
Ok, all spark plugs are black with soot. No oil on the spark blacks just dry soot.

You may find this thread useful, sounds like we had similar problems.

LINK (http://www.kiwibiker.co.nz/forums/showthread.php?t=47143)

kneescraper
9th April 2007, 16:44
Ive read the link, cheers Dan.

How did you clean the oil off your air filter?

Also if it was the air filter being gunked with oil how come the bike would drink so much fuel..the filter wouldnt determine how much fuel the carbs need. The usage of fuel should be the same no matter the condition of the air filter, the power would be affected if air filter was at fault...isnt this correct?

I still think its the carbs....

Disco Dan
9th April 2007, 16:52
Ive read the link, cheers Dan.

How did you clean the oil off your air filter?

Also if it was the air filter being gunked with oil how come the bike would drink so much fuel..the filter wouldnt determine how much fuel the carbs need. The usage of fuel should be the same no matter the condition of the air filter, the power would be affected if air filter was at fault...isnt this correct?

I still think its the carbs....

I cleaned my filter using K&N filter cleaner - basically a mild detergent.

The filter was restricting the amount of air getting to my carbs at high rpm. However they now dont get enough fuel at high rpm.

When was the last time you replaced your fuel filter? You may also want to clean the strainer in the fuel tank? (remove the fuel tap and clean the strainer with compressed air)

Have you checked for a vacuum leak anywhere? Take the plastic covers off the carbs (verycarefully) and inspect the rubber membrane for rips. Check all hoses, especially ones that get hot and at the joins - if any joins seem too hard, cut the end off and re-attach to create a better seal.

merv
9th April 2007, 16:52
Is it a foam air filter then? You can buy filter element cleaner in a spray can from the bike shop and spray on oil to treat the filter. I'm using PJ1 stuff at the moment and it is OK.

When I was a lad we just used petrol to clean the filters then wash them out under a tap, dry it in the sun and then re-oil it with car diff oil SAE90 kind of stuff, but these days you can buy the right stuff.

Disco Dan
9th April 2007, 16:55
Is it a foam air filter then? You can buy filter element cleaner in a spray can from the bike shop and spray on oil to treat the filter. I'm using PJ1 stuff at the moment and it is OK.

When I was a lad we just used petrol to clean the filters then wash them out under a tap, dry it in the sun and then re-oil it with car diff oil SAE90 kind of stuff, but these days you can buy the right stuff.

Yes, what they dont tell you though is how important it is to let the filter dry 100% before you re-oil it! You can trap moisture in the filter, suck water into the carbs... all sorts of nasty sypmtoms happen then!

kneescraper
9th April 2007, 17:08
Thanks for the comments guys but I think we are missing an important point here. There is to MUCH fuel...its doesnt hesitate, doesnt run bad...it uses tomuch fuel...If the fuel filter was dirty then it wouldnt get enough fuel (btw the fuel filter is real clean), the bike is getting about 3 times to much fuel from my calculations...how ever it is still running fine. But also when an engine is running rich it loses power so Im thinking its down on that too,

Kickaha
9th April 2007, 17:10
Also if it was the air filter being gunked with oil how come the bike would drink so much fuel..the filter wouldnt determine how much fuel the carbs need. The usage of fuel should be the same no matter the condition of the air filter, the power would be affected if air filter was at fault...isnt this correct?

This is straight from the Ryco filter site

When should I change my air filter?

A blocked air filter can significantly increase fuel consumption. In addition, it can increase cylinder bore wear due to excessively high fuel to air ratios.

and this from K & N

http://www.knfilters.com/audio/09%20Mileage.mp3

kneescraper
9th April 2007, 17:14
Ahhhhhh I see....the engine must work HARDER to suck the air...hence the increase in fuel use...ahhhh

I stand corrected!

Thats a great link, cheers Kickaha

merv
9th April 2007, 17:21
Where's NM when you need him, he perhaps needs to tell you what he had done to the carbs? If I remember rightly he was talking about the bike using a lot of gas back then but I would have thought he had it cured.

How'd did Jim2 go with fuel use riding it up?

There's a big difference between air filter and fuel filter and mainly we were talking about air filter.

kneescraper
9th April 2007, 18:14
NM has explained to me what has been done, the carbs were stripped and then rebuilt. I think Jim2 had the same experence that Im having, high fuel useage.

I will change air filter element tomorrow and see what happens.

RT527
9th April 2007, 18:32
Ahhhhhh I see....the engine must work HARDER to suck the air...hence the increase in fuel use...ahhhh

I stand corrected!

Thats a great link, cheers Kickaha

Actually its not working harder to get the air in, whats happening is that there is a significant reduction in air to fuel mixture so its pouring too much unburnt fuel through the carbs, check the back of the cans to see what colour the soot is if there is any....dark black around the end means lack of air, a light grey may mean too much air....I think if i remember right .

Ixion
9th April 2007, 18:32
Uh, the choke's not stuck is it? Sure ?

Motig
9th April 2007, 19:30
Did you do the obvious and go for a ride without the airfilter then check the plugs again ? Would show if its a blocked filter then.

kneescraper
9th April 2007, 20:01
I didnt go for a ride, I did rev it and let it run for a couple of mins. I was running out of sunlight fast...also had to cook dinner :).

I will replace the air filter tomorrow...that is a small cost so it doesnt worry me. No the choke is not stuck on, I checked that.

Cans? I guess that means exhaust...the exhaust is very black..blows desent amount of black smoke when I rev it above 6,000rpm....it redlines at 13,000rpm so im not over reving it.

JimBob
10th April 2007, 07:59
""when NM was refitting the carbs or when they were rebuilt""

Try a new aircleaner element and if that doesnt sort it I would find out what "rebuilt" means. If someone has been monkeying around with the carbs get them back to the standard setup and take it from there.
cheers

kneescraper
10th April 2007, 18:52
Well I fitted a brand new air filter today, I ran it for a 5 min ride with out the air filter so it cleaned the spark plugs up (as one KB'er told me too) and re-checked sparkplugs, they were still dirty. As it was getting very dark I called it a night, took it for a ride..it pulls stronge and sounds normal..same as before. I am yet to see if the fuel usage changes, however if the plugs are anything to go by it hasnt changed.

James

merv
10th April 2007, 19:01
The fuel usage will tell you how rich it is running, but one thing to remember these days is don't be too fooled by the plugs. In the old days they would burn what we thought was clean - all nice and white looking - but that was with leaded fuel and it was actually the lead deposits we were seeing. Nowadays with unleaded they always look a bit black as does the exhaust outlet. In the old leaded days the exhausts after a long run would look clean and white at the outlet too, but not now they are black.

If its still too rich with a decent aircleaner it can only be the carbs. I was hoping NM could give you the lowdown - but does if have the correct jets, are the needles set in the right position, are the float needle valves set right? There aint much else you can check if it is running well and it aint an ignition issue. Any other problem it would be running like a bag of arseholes - misifiring, spluttering, all that kind of stuff.

kneescraper
10th April 2007, 19:06
Yeah, I am to ring Wellington Motorcycles tomorrow and ask Chris? what was done and if all was done right...not that he would admit it if it wasnt...we are humans after all.

nudemetalz
11th April 2007, 20:54
Ummm,...he did redo the carbs. He showed me exactly what he did and pointed out all of the o-rings that were replaced.
He's a bloody good mechanic, I wouldn't accuse him of not doing his job ay.

I wonder if the choke valves are stuck inside.
When I put the carbs back on and was sure that the choke cable went on and functioned as normal, but just wonder if they're not settling down correctly, ie a little bit on still when the choke lever is off.
Try taking off the choke cable completely from the carbs and see how that goes.

JimBob
12th April 2007, 09:02
After firing the bike up, did the idle speed and mixture set up easily?
ie the idle fuel adjustment isnt way different from stock adjustment?
Why did they need rebuilding?
Was this problem there before the carb rebuild?
What does "rebuilt" mean?
To sort these carbs out strip them down, note all settings, clean and reassemble to stock specs. ie needles, positions, jets, float levels, the lot.
If a choke is on once you are over 1/4 to 1/2 throttle it has little effect. (I am presuming these carbs have enrichners rather than chokes)
good luck

Disco Dan
14th April 2007, 19:24
The sparkplug is covered in black soot....stinks too hehehe The electrode? is also black...very black.

Thought you may need this....

http://www.kiwibiker.co.nz/forums/showpost.php?p=1013151&postcount=13

Bling to Drum for that post!