Bike Carb help Needed!

[Tazzzzman1]

Hoping some one on here can help?

 

I have fitted some Fireblade carbs to the car. Had her running (all be it very roughly) last weekend, however now she will not start or even attempt to fire up.

I have done the basics, checked sparks (no problems) Checked timing (Ok), but spark plugs do seem to be a bit on the dry side, so I'm not sure it's getting much fuel through.

Plenty of fuel in float chambers though.

Stripped carbs apart, cleaned out again, still no joy

 

Any suggestions from anyone who has fitted bike carbs? I'm out of ideas.....

[Bob Tucker]

Sounds like lack of fuel....sure youve got any in the tank?????

 

if youre running an electric pump make sure its actually pumping...disconnect a fuel pipe into a container & switch ignition on briefly.

 

If its the engine driven one squirt neat fuel down the 4 carb throats to get the engine running & prime the pump. If it wont fire then, its electrics.

Bob

[Guest woolly]

might not start from cold if you don't apply the cold start (choke mech)

[Dave R]

how long have the carbs been off the bike?

on mine, the fuel was that gummed up, there were no holes in the jets

[Andi]

might not start from cold if you don't apply the cold start (choke mech)

 

Second that.. Some need it, some dont.

Also dont forget the painfully embarrasing common mistake of having the fuel pipe in the wrong hole

[Guest gdc]

having it the wrong hole is going to hurt ,]

 

and someone will notice .eventually

[Tazzzzman1]

Thanks all, But done all of the above already...

 

Going to carry out a compression check today, just to make sure that I have not dropped a valve/ piston.

Dan is coming over tomorrow with his carbs so we can do a swap. At least this will tell us if it is the carbs or something else.

My gut feeling is a carb issue as there seems to be very little fuel getting through. What is worrying me though is that even with fuel poured directly down the carbs isn't making her cough either

[Bob Tucker]

What is worrying me though is that even with fuel poured directly down the carbs isn't making her cough either

 

Has to be electrics somewhere then.

Just because you gat a spark doesnt mean its sparking at the right time.

Even an engine with really low compression wil still fire.

Losing just one cylinder with dropped valves will still fire the other 3.

 

Best of luck with it

Bob

[Tazzzzman1]

Has to be electrics somewhere then.

Just because you gat a spark doesnt mean its sparking at the right time.

Even an engine with really low compression wil still fire.

Losing just one cylinder with dropped valves will still fire the other 3.

 

Best of luck with it

Bob

 

 

Fingers crossed..

What I can't work out is that the timing has not changed since I was running the car last year...All I have done is change the carbs. Which iSs why I'm thinking more of a carb problem. However when it was running porr last week I did attempt to drive it to get the Carbs sorted, but she was running so bad I drove her back home. Hasn't started up since...

[Tazzzzman1]

Update:

First of all a big thanks to Dan (Notimpressed) Who has been with me all day doing some serious head scratching.

Swapped his carb set up on to mine, still wouldn't fire....hmmmm

 

Checked Compression and found all cylinders were only 30-90 psi...what the f@@k

 

Checked valve timing and found gaps were non existent on 3 cylinders. Re adjusted and hey presto she fired up straight away although No 4 carb was spitting and popping well.

Re-checked compression and got the following results:

No 1 cyl = 175PSI

No 2 Cyl = 170 PSI

No 3 Cyl = 172 PSI

No 4 Cyl = 90 PSI....ouch

We can't understand why this has changed, everything was fine when she was parked up for the winter.

 

Did the oil test by pouring oil into the spark plug hole and retesting, went up to 150 PSI....looks like I have a piston/ ring issue on No 4 cylinder. :

Only just got the engine back in now looks like it's back out and a bit of rebuilding to do.

 

Might also explain why I have had so much crank case pressure forcing oil through filler cap?

[Bob Tucker]

Pull the head off before removing the engine. The problem could be there. You can also check for ridges/scores in the bore.

I had a problem losing valve clearance & compression on 2 pots....turned out to be cracked valve seat inserts which I had fitted to convert a leaded head.

 

everything was fine when she was parked up for the winter

One more nasty thought...You did have antifreeze in over winter?

A cracked block could give the same symptoms...

[Tazzzzman1]

Hi Bob,

Hope to have the head off tonight...Will have a good check.

Would have thought though that cracked valve seats would have lost compression? Mine are now back upto 170+ psi. It's just Cyl 4 which is low. seems to come back up when adding oil to the bore.

 

Definately some food for thought though. I will be having a close look at the head when shes off. Fingers crossed it's something simple.......and not too expensive!

Sun's out and I want to play.......

[speedtripledan]

Hi Bob,

Hope to have the head off tonight...Will have a good check.

Would have thought though that cracked valve seats would have lost compression? Mine are now back upto 170+ psi. It's just Cyl 4 which is low. seems to come back up when adding oil to the bore.

 

Definately some food for thought though. I will be having a close look at the head when shes off. Fingers crossed it's something simple.......and not too expensive!

Sun's out and I want to play.......

 

double check no4 with an open throttle mine raised by 50psi with open throttle all sorted now