F3 Problems

[merlin]

Allrighty- I picked up Dyscofool's F3, replaced the fuel pump with the slightly different part out of my Hurricane. Got her running and idling. So far so good- Now I am running into a different problem, was wondering if anyone here had any ideas:

When I take off, the bike jumps, chugs and just barely runs at all. I have to feather the clutch and keep the RPMs up around 3K just to keep it from dying. If I stay in the throttle, it will eventually lurtch and jerk it's way up past 5K rpm- where the motor smooths out and starts to run more normally. At 7K when I hit the powerband, she takes off like a raped ape. Same progression in every gear- stutters, chugs and almost dies under 5, runs a little rough but not bad from 5-7, and perfect over 7. I am thinking the problem is in the carbs, my mechanic buddy thinks it's still the fuel pump, and I haven't heard what you think yet. Any ideas?

Oh- one other question: Does anyone know if the F1 and F3 use the same cam chain tensioner?

Merlin

[NineTwoFour]

I would rejet the thing... sounds like one of the low speed (I think that is what it is called) jets is plugged up.

Also check your plugs to see if they are fouling... if you haven't changed them already, you may consider doing that.

[Devil954]

I think you need to buy the motor I have :lol:

[merlin]

I think you need to buy the motor I have :lol:

Well, after the bike, the helmet, a timing light and dinner last night, I have $5 left out of my insurance check.... I'll give you that for it ::grin::

Merlin

[(( LO LO ))]

How are the fuel lines? Are they unobsturcted? Maybe the fuel pump isn't pushing enough fuel through the lines at low RPM's because the fuel lines might be gunked up. Then when the rpms go up, the pressure made from the pump might increase causing the fuel to flow better. I'm no expert. :? Just a thought....

[MattTLS]

It does sound like carburetor problems. If the bike sat for quite a while, the smaller jets are probably varnished over. Take it apart and give them a good cleaning.

Matthew

[irdave]

Er, my '94 F2 doesn't seem to have a fuel pump... It's gravity fed out of the bottom of the tank directly into the carbs...

But it does sound like it could be the slow/idle jets. It's too easy to check to pass by without doing it.

[Anonymous]

Definitely sounds like fuel delivery, I'd rebuild the carbs for good measure (i.e. clean them out very well, replace the wearable components like the diaphragm, etc), and you may as well jet it while you're in there and save yourself the trouble of doing it later.

While you're at it, replace the fuel lines (a few feet of fuel line at checker will set you back about a buck and a half). If you have a vacuum-controlled fuel feed replace the vac line as well. Rubber just wears out after a while.

Toss some new plugs in (they're cheap too), make sure you have a clean air filter, make sure the plug wires are in good shape ... that should get you running in top shape!

[merlin]

Allrighty- I think I found the problem.

I got the carbs off, took the float bowls and diaphrams off, and cleaned hell out of everything. So far so good. I did notice that I am aparently running 2 different size jets- 1 and 2 are 138, 3 and 4 are 140. Not sure if that is normal or not (somehow I doubt it)

I got to doing some other testing, and found this: inside the float bowl, there are 3 brass thingies (I know fuck-all about carbs... can you tell?) One has what I assume is the main jet screwed into it, one has a screwdriver slot and comes out as a unit (that one is marked 40S on all 4) and one has NO screwdrive slot and I assume does not come out. I hooked my handy-dandy vacuum pump to the one with no screwdriver slot, and lo and behold, #2 and #4 are holding vacuum. Plugged up (or it is SUPPOSE to hold vacuum, in which case #1 and #3 are leaking) Now here's my problem- since that structure does not appear to be removeable, and I am concerned I'll bitch something up if I try and clean it out with a long thin thing (like the bristle off a broom, for instance) and carb cleaner does not seem to have any effect at all.... Now what?

Merlin
-On foot till I get this fixed

[Anonymous]

I assume these things you're testing with vacuum look like they have holes in them for a reason? (can you take a pic?) Try some stiff wire, and let some carb cleaner soak in there for a while to get the gunk out.

[merlin]

I assume these things you're testing with vacuum look like they have holes in them for a reason? (can you take a pic?) Try some stiff wire, and let some carb cleaner soak in there for a while to get the gunk out.

Wish I had a digital camera... Yeah they look just like the pilots, just without the screwdriver slot (they are right beside them too). I am trying to figure out how to go get some more carb cleaner now. I tried thin wire and broom bristles- too big. If I could figure out a way to get them out, it'd be easy. Trouble is, they don't appear to come out.

Merlin

[Dysco]

Take the old carbs and do the same thing before you do anything rash.

[merlin]

Take the old carbs and do the same thing before you do anything rash.

I actually got it cleared- one strand out of a speakerwire was just the thing.

Now if I can just get all the air lines connected to the carbs and airbox correctly, I think I got it licked.

Merlin

[Anonymous]

Personally, I'd still go soak every metal part from that carb in cleaner for a little while to get all of the varnish off, before you slap it all back together...

[RCStylin]

Guitar strings (the high "E" small one) work very nicely for cleaning jets for future reference :idea: