carbs or filters

**aff-man** · 5th August 2003, 10:41

Talking to some guys on the weekend about my carbs not geting enough air through the 7-9k range and had a though.(Amazing isn't it) But here goes could it perhaps be the air filter. If it's not letting enough air through due to being old and crappy would that be maybe the problem and nothing actually wrong with the carbs. Or am i way off base. Any thoughts. Another thing is, is there a way to test if it is the filter without taking it out and shit getting into the engine. I was thinking a thin porus foam substitute??

**Dave** · 5th August 2003, 10:51

What does your bike rev out to,you said it's not right in the 7-9k range, but does it run alright after that? if so,then it aint an air problem.
For the purpose of diagnosing,remove the filter,warm the engine and run it up the road-it won't cause any harm.
what are the symptoms? does it miss or just go flat?

**aff-man** · 7th August 2003, 09:46

After 9k the thing takes off like a bloody rocket. The symptoms are as follows:

1- after about 7k the power eass off big time like almost nothing the needel inches it's way up to 9k then the big takes off.It's also worse in cold wether sometimes even getting passed 7k is impossible. To fix this i just full ckoke it and it seems to run ok. Also not so noticeable when bike it warmed up.

2- Unfortunatly my 100-105k cruising speed it +-8k and if i try and sit at this the bike sort of "bucks" i don't really know how to explain it it's like it's fighting to get air and like taking it in gulps when possible. Turning on the choke also fixes this.

BUT and there is always one, If i turn the coke on full the bike does not idle at higher revs like it's supposed to but rather the revs go down untill it dies out hence having to use throttle control to keep the revs up if the choke is on.

After asking the mechanics they said it could be the slider thingy's in the top of the carb. Now the rod they sit on is meant to have adjuster ring with slits to make it richer or not but aftet taking apart the old carb i found this was not the case. So if i need to put in a spaces does anyone know the dimensions????

**Dave** · 7th August 2003, 09:52

Right, I can tell you straight off its horribly lean on the needles.
Do your carbs have rubber diaphragms in them attached to the pistons? if so they are probably stretched or split.check that.
The air is not an issue or it wouldn't take off after 9000.
don't worry about the no idling on full choke,if anything maybe less choke on warm up would solve this.
good luck-keep us posted.

**gpercivl** · 7th August 2003, 11:11

I agree with Dave, a 'hole' at that rev range is quite often needle setting. If they're currently on the middle setting, you need to raise them at least 2 'clicks' to get an appreciable difference. Just about all Jap bikes are set super-lean to meet emission rules when the carbs are partly open and respond favourably to richening (in my experience).

**wkid_one** · 7th August 2003, 18:03

Agree - my 250 Bandit had exactly the same hole in the same spot - and re-doing the needles fixed it

**aff-man** · 7th August 2003, 20:48

By the way <-- This is the bike. Now i know i should find a manual somewhere but the needle is the rod with notches that the u shaped clip can be changed up or down to richen it. But here is my problem the needle on the old carb didn't have any natches it was a fixed seting sooooooo before i take this carb to pieces i need to find out how big the spacer is that i have to make, if i need one????

**Kwaka-Kid** · 7th August 2003, 21:10

just grab a few tiny washers, about 2x or 3 for each needle :P nah just try 2 odd for each needle and raise em up, that will lift the needle out of the jet thereby letting more petrol in (risher) this is my GUESS and what i did to my GPZ750, altho not hte washer trick, but it will work and will save u money, im sure it will? the theory is tehre right? if the old washers of different sizes u got arounfd home done fit in somhow, rip out a small file and file a nice notch out of ur carbs whereever its catching, or at least thats the KK way of doing it.

**MikeL** · 7th August 2003, 22:29

Originally posted by Kwaka-Kid
or at least thats the KK way of doing it.

What would we do without you, KK, to remind us of our gung-ho, can-do, number 8 fencing wire approach to life's little problems? Far too many of us trust the experts, and are afraid to be seen as fools rushing in where angels fear to tread...
We are talking about tap washers, I presume??? Or do you mean those metal ones? And if the file thingy doesn't work, do we just get out the hammer?
I wish I'd realized earlier that bike maintenance was so simple - I would have saved myself a fortune.

P.S. The above contains a very slight touch of irony and is not meant to be taken (entirely) seriously. I just thought I should spell that out.

**bikerboy** · 8th August 2003, 14:13

Whatever you end up doing Aff-man, please, please do not follow KK's advice.

I'd really hate to read about "some student's" bike exploding in the Tech parking lot!

You need someone who knows what they are talking about, Dave..?

**Motu** · 8th August 2003, 18:27

I'm not too sure what you got,but the needles should still come out,they aren't part of the slide.For washers use some wiring terminals - go to Repco and get a packet of the red lug terminals - 5mm sized lug....now chop off the red bit that takes the wire - hey,lookit that,you now have some very small washers! One per carb,test,do it again maybe?

**Kwaka-Kid** · 8th August 2003, 19:13

bah just look in the garage. everybody has a icecream container full of all sizes somwhere.

as i said, if a few are diff, who cares.

or do it motu's way, and waste $3 or som rediculously expensive price like that, for what they are. You know for $3 you could get 3x nice Cheese scons from work on mondays? yeah thats right... think of the scons...

**bikerboy** · 8th August 2003, 21:06

It's official, madness rules KK land with an iron fist !

**Motu** · 8th August 2003, 22:52

Hey KK,I've got a whole workshop full of little boxes of odds n ends,but no tiny washers.When Sanyo closed down over the road,we went over and lifted piles of weird shit,but no tiny washers.I got 500 2amp fuses and rolls and rolls of wire and terminals,but no tiny washers.I'll swap ya 300 2 amp fuses for 4 tiny washers!

**Big Dog** · 9th August 2003, 01:49

Though obviously unrelated there is no cheaper way to get a new lease on life than new fuel and air filters. According to a magazine we used to get at the car yard most oem filters ar designed only with run in periods in mind as these should be replaced at first service but most are not. These cheap often very oily filters are also designed to lean out the mix for emmisions testing

The last time I replaced both they were less than thirty dollars for both at repco. (that was for a gpx 250)