SRX600 and keihins

[Steve H]

After a few false starts and a lot of petrol spread over the engine (duff 'o' rings) Ive finally got the SRX fitted with the Keihins started. It runs very rich at low revs, but does run. I did however notice some odd behaviour. I could just about get it to tickover after starting it, but then when I put it on the side stand, it would die. When I set the tickover to be correct on the side stand, then lift the bike the revs rise up to around 2000 rpm then drop back down again.
I suspect float height but its been set (and checked several times).

[themoudie]

Twin carbs with two seperate float chambers Steve?

Not like the old set up with just one float chamber, would this make the difference?

Does the cant on the sidestand make a float (or both) stick on its pivot, so preventing the float needles from seating at the same time?

Is the rubber tip(s) on the float needles ridged or worn, preventing seating?

Is it possible that one carb is partly starved of petrol by the other, because the fuel tap/line isn't of sufficient bore to match the fuel flow requirements of two carbs?

Are the filters in the tank or line chocked?

I hope you can find the cause Steve.

Regards, Bill

[Steve H]

The multiple float bowls was my initial thought, but then I realised that virtually every other bike with multiple float bowls would exhibit the same symptoms. I theory the float valves should stop any problems dues to height differentials.
The tap might cause problems at higher loads but hopefully shouldnt cause problems at light loads.
I was knackered last night after spending ages trying to start it, I shall look at it again with a more level head during the week.

[peterj]

Only thought is that if you don't have the idle circuit dialled in right, the idle adjustment could be very sensitive, and the extremely an small difference in fuel level may change the idle speed considerably. Or (unlikely) something unconnected with the fuel entirely such as bars move when you take it off the stand and throttle cable moves around a bit?

What did you do about the the throttle linkage btw? When I tried ones off a GPX250 (supposedly same as a ZZR) the throttle linkage (well the cable termination bit at least) wanted to live inside the petrol tank. I haven't bothered to modify mine and try again yet.

[GB500nz]

Most bikes run better upright. lying over on the sidestand, you wouldn't expect it to run properly, would you?

[Steve H]

Most bikes run better upright. lying over on the sidestand, you wouldn't expect it to run properly, would you?

Why would it not to run as well on the sidestand ?.  Fuel level in the bowls will probably be slightly lower but I cant see that making 500rpm difference in tickover, and the jets pull from the centre of the bowl so wont be starved of fuel.

[themoudie]

Aye GB500NZ,

I would expect a bike to tickover on its sidestand. B****y annoying if it wont when I am dealing with gates, having a slash behind a bush or removing the wasp from down me neck. I can understand why competition bikes of an older persuasion might not, but Steve's set up should!

I hope your winter isnt being foul. Not long for your shortest day now and the return of the current bun. Also a real bummer "Bruce Anstey went out on the first lap when a £40 ignition amplifier failed on the Relentless Suzuki." I hope he does well and is safe along with all the others racing this week.

Cheers, Bill

[andy230]

After a few false starts and a lot of petrol spread over the engine (duff 'o' rings) Ive finally got the SRX fitted with the Keihins started. It runs very rich at low revs, but does run. I did however notice some odd behaviour. I could just about get it to tickover after starting it, but then when I put it on the side stand, it would die. When I set the tickover to be correct on the side stand, then lift the bike the revs rise up to around 2000 rpm then drop back down again.
I suspect float height but its been set (and checked several times).

Hello Steve

Mine doesn't do this.  I figure it would be bad to tip into a corner, on a closed throttle...!!   WAAAAAH... (off into the green stuff...)

Not sure what it could be tho... cables sounds like a good bet, but I'm sure you've checked those.  Sticky floats?  Never checked or adjusted the float hight on mine.

I use the standard vacuum tap, with the pipe from the inlet manifold, no probs either at low ot high engine speed.

can give a wee bit info on jet sizes etc...

a

[Steve H]

Andy, thanks for that. I meticulously recorded all the jets I used, and then equally meticulously lost the bit of paper, once I know what Ive got fitted Id be intersted in knowing what you are running. I'm going to strip the carbs of again and check all the rubber seals, the ones on the float valve were solid, so it may be fuel leaking through a seal somewhere.
Ive also bought a cheap 4 wire lambda sensor which once the bikes running a bit better I will wire up to check full throttle etc.

[OMEGAMAN]

If it's of any use to you,  My 620cc race bike runs twin 33mm kehin CR carbs & runs fine with 130 main jets,

Have to admit I have no sidestand though!

[Steve H]

Current jetting is with openish exhaust, standard airbox and K+N, stock piston and stage 1 cam.
Pilot 58
Main 130
Air 220
Slide 2.5
Needle Y9

I was emailled these settings quite a while back, they were from a bike Martin Sweet had set up. The main difference is the pilot jet which was supposed to be a 40.
Andy/Omegaman how do these compare with your jetting

[OMEGAMAN]

Current jetting is with openish exhaust, standard airbox and K+N, stock piston and stage 1 cam.
Pilot 58
Main 130
Air 220
Slide 2.5
Needle Y9

I was emailled these settings quite a while back, they were from a bike Martin Sweet had set up. The main difference is the pilot jet which was supposed to be a 40.
Andy/Omegaman how do these compare with your jetting

Getting a bit too technical for me!   I just read about the main jets in the paperwork that came with the bike!!!!!

[andy230]

Current jetting is with openish exhaust, standard airbox and K+N, stock piston and stage 1 cam.
Pilot 58
Main 130
Air 220
Slide 2.5
Needle Y9

Will need to check my log book for the others, but wfor the mains... With an airbox but no filter a 118 was about right.  A K&N panel filter in there made it too rich, meaning blips for downchanges just died (and the back end squidges around everywhere as you let the clutch out & try to get the plot straight again!).  It was a little lean on 118s (filterless airbox, but with a modified lid), so when I took it out I went up to 125s.  In testing the plugs looked a little white, so I went to 130s, with just carb trumpets.

I think mine has a Stage 2 grind on the cam, a hi-comp piston, flowed head, and the straight thru pipe with big can.  Will confirm other setting when I get a look at the magic book.

Cheers

a
 

[andy230]

  Will confirm other setting when I get a look at the magic book.

Cheers

a
 

Gaaah!!  Keep forgetting!  Will post soon!

a

[longdogcymru]

Please enlighten me, are these the standard carbs that are fitted here or are there accepted mods, even a single carb that will fit?