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Sherco 4t Carb Flooding


atomant
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Seem to have the starting thing sussed now except..... If the bike is up ended in a section so the bike is near vertical, the engine will cut out and the fuel floods out into the airbox. After which the bike is a bitch to start! same thing happens if I lay it down.

Looking at the float arrangement, its easy to see why it does this as it has 2 floats both sliding on 2 pins which will be fine when upright. When at an angle of 90degrees, the floats will be forced up putting side load onto the pins and stop then from sliding.

Is the Kehin carb like this? Are there any other carbs I could fit that dont have this problem. Mating the different carb up wont be a problem for me as I can design and make new adaptor/s

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The 2T carb has much the same arrangement, two floats which slide up and down two pins per float!

I had mine out yesterday and she was difficult to re-start if stalled, OK if you shut the motor using the kill switch.

Mine has always been ok to start when stopped using with the Kill switch.

This is the ONLY problem the bike has left that needs sorting,

once this is done, its as good as it gets and thats awesome :D

In my biased opinion of course :lol:

Oh and by the way, wouldnt get this problem with fuel injection !!!

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Hey Webmonkey

Just have got my 4t fitted with a Keihin PWK28 and jetted by Howard Wallace and I can notice that the engine is running a lot smoother and easy to start cold now as you dont have to keep the choke on like the Delorto did until the engine was hot. The keihin fits straight in with only a small modification on the cable adjuster out the top of the carby and a couple of drain hoses, it looks very neat.

I am running the bike in a trial at the comming weekend and will let you know my thoughts after 50 sections and a full day with it.

The keihin's float hinges on a pin not like the Delorto, see for yourself on

www.carbparts.com/keihin/pwk_28_expl2.gif

Cheers

Johnnysherco

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Sounds good - Try lifting the bike to near vertical (up a steep bank or something)and see if the bike cuts out - if it does, then try starting it again on the flat and tell me what happens - if it starts then im buying one :lol: also, if you could let me know what Jets Howard put in it that would be a great help :D

I did however notice that one of the minders at hawkstone was running a Kehin carb on his 4T and still had a problem starting it.. so I need to be sure about this one before I fork out some dosh.

Many thanks

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Sounds good - Try lifting the bike to near vertical (up a steep bank or something)and see if the bike cuts out - if it does, then try starting it again on the flat and tell me what happens - if it starts then im buying one :lol: also, if you could let me know what Jets Howard put in it that would be a great help :D

I did however notice that one of the minders at hawkstone was running a Kehin carb on his 4T and still had a problem starting it.. so I need to be sure about this one before I fork out some dosh.

Many thanks

My gas gas pro 02 fell over off the side stand . I didn't notice and when i got back the air filter housing was full of fuel. It's a common problem with the delorto but the bike will not start straight away as it's flooded

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Webmonkey,

For starters stop tipping the thing upside down mate :D

Try lowering the Dellorto float level a mill at a time, by measuring from the bowl face to the tangs that close the needle. Sure this will fix your problem.

The KeiHin when set up, will still run when the bikes lying on its side, and when balancing up a brick wall with the handlebar crossbrace against your chest. That`s about as close to a test that I can give you, to compare. As long as your brick walls are as steep as ours.

Running a 40 pilot 110 main and a JJJ needle, and if you want more top end run a 120 main.

Edited by Howard Wallace
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WM

i have drilled a small hole in the air box and fitted a short length of clear tube with a blank on the end

now if fuel or water accumalate in the air box firstly i can see it and secondly i can get it out without tools

just make sure it is air tight

i have no probs with mine now

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Just fitted the KeiHin and been riding the bike up and down my drive for a bit and so far it looks real sweet. Easy to start even if i stall it ( purposely you understand :) ) Just up ended it against the garage wall and it didnt stop. didnt flood, didnt mess up at all !!!

Ill see what its like after a week or two! :D

Oh and by the way, ordered it 3.20pm yesterday from Allen Performance. They set it up and shipped it and got it at 9.10am this morning :lol:

Good service that !

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Webmonkey,

the JJH will be close to the mark.But I had to run it on the top clip, the JJJ runs on the middle clip, and feels more progressive. Interested to see if you notice any difference in fuel usage.Just read a factory email recommending, inlet at .13 instead of .15 ,and idle set at 1,300. Will be having a play with these settings.

Let me know if the KeiHin keeps it running when the bikes upside down.??? :D

Edited by Howard Wallace
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Well initially it was running sweet when I took it up and down my drive. But, when i took it out for a blast, it wouldn't rev to full throttle and was missing a bit. I spoke to Allen Performance and they suggested I go to a 125 Jet which I will try today (Friday)

Howard, what is the air screw setting you used by the way.! I have it fully in then anti clockwise 1 full turn. If I release it any more, it farts and pops away. If I take it to nearly half a turn I get a very responsive increase/decrease in throttle control better than the dellorto was on its factory supplied setting. Is this in too much?

I currently have the needle on one setting down from the top clip!

Are you expecting it to use more fuel ? I would have thought so if Im increasing the main jet size. What do you think?

Also, having taken the Dellorto off and taken a look at it, There is a small pipe, bottom centre on the inside of the rear air inlet port.

If you hold the carb level and keep rotating it until its at an angle of around 60 degrees , fuel pours out of it like a tap. If I block this off then fuel just comes up out the main jet and floods back albeit much slower. Why design it so it does that!!! Why not put in small solenoid valve which shuts off when the motor stops.

90% of my problems I have had with this bike is due to this. :wall:

UPDATE fitted the new #125 jet and seems to be ok now although the bike is running a bit hot as the fan isnt cycling on/off anywhere near as much as it was. :blink:

Edited by Webmonkey
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Just come back from my first trial with the KeiHin on and have found the bike is running MUCH hotter than with the dellorto. Dont know if its coz im running richer jetting or not.? The fan is on constantly and doesnt cycle at all.

Its been a bitch to start a few times and I never had this hot start problem with the Dellorto :blink:

Probally try the Dellorto again but change the jetting and mod it so I dont get that overflow problem into the airbox again.

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The pilot screw should run between 1/2 to 1 1/2 turns out, so your pilot is about right.The popping is lean mixture .When you wind the pilot screw out, you are letting in more air.

Fans on more often? hotter day? or the fuel mixture is burning hotter ,due to a leaner mixture, compared to the Dellorto. Wouldn`t worry, as temp wise it wouldn`t be much higher, as long as it`s not boiling, it will be fine.

Dave, will check with factory on those valve settings, E-Mail states admittance valve,I assumed that`s the inlet, but may be different to the Spanish

Edited by Howard Wallace
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Howard,

The fan was on all the time and doesnt go off. The ambient temperature was around 22 degrees so it wasn't that hot. I wouldnt have mentioned it but it is in stark contrast to what I had before.

Have you any experience with the Mikuni carbs - this TMS38 carb although maybe need some work to get it to fit has a nifty Pro-Option which sounds good ! its at the bottom of this page http://www.motorcyclecarbs.com/mikuni/TMX35_settings.htm

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