Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: guest1406 on December 09, 2014, 02:00:22 PM
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Hi all,
Think I’ve just figured out how to post pics. This is my slow build:
(http://i62.tinypic.com/2r62x5z.jpg)
Started off as a 2003 Suzuki Van Van, mods include:
- GN250 engine, top end rebuild with a 300cc barrell and piston and gasket change
- Spec made Lectron Carb with K&N Filter
- Extensive frame modifications for engine fitting
- Rear frame loop
- Relocated hidden battery box
- Hidden electrical box
- Relocated ignition switch and headlight switch
- Remote front brake master cylinder
- Custom made hidden simplified wiring loom
- Ball end levers with indicator toggle switches built in
- Mini Koso speedo
- Bates style headlight with yellow vinyl wrap
- Two into one wrapped high exhaust
- Powder coated satin black
- Bare metal 2.4 gallon Harley Sportster tank
- Bare metal narrowed mudguards
- Custom fiberglass seat base and seat upholstery
So today I decided to get her running right and she just would not start. Its turning over and I can her the starter motor working it’s just not igniting. I haven’t checked the spark plug yet but it is brand new.
However when I place my hand over the carb mouth, the power valve (line on the right of carb) fuel level rises, starts but won’t idle then floods the carb mouth and cuts out.
(http://i61.tinypic.com/i5zuvp.jpg)
This is the fabricated intake manifold to accommodate a carb:
(http://i61.tinypic.com/2v7vt6v.jpg)
This is the angle of the carb
(http://i58.tinypic.com/ih08ir.jpg)
Is it possible that it’s too much of an angle? But I’ve seen Lectrons work at extreme angles too.
Appreciate any input,
Mackenzie
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The fuel level looks a bit low but assuming all the fuel feeds are covered then it shouldnt really effect starting too much.
Is the thing on the top the venturi (with a screw in it) the main jet or idle jet ?.
If it starts when you put your hand over the inlet it suggests that there is insufficient depression/vacuum in the venturi to pull fuel up the line. I would suggest fitting a conical filter K+N type filter to start with, that may at least create enough vacuum to draw the fuel up that far at idle speeds. once its started you can go from there.
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The fuel level in the pipe leading up to the power valve looks way higher than that in the float bowl. Curious. One would have thought the levels would be in line?
Do these carbs have a dedicated idle circuit? It's been a while since I read about them but I seem to recall that they don't?
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Have you read the Lectron Tuning instructions ? HERE (http://www.lectronfuelsystems.com/docs/Tuning_Instr.pdf)
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Cheers steve H.
The power jet is only meant to come into play at very wide open, high air flow conditions. When the hand is placed over the inlet this would seem to be the exact opposite! Except, of course, that the obstruction to air (the hand) is on the opposite side of the power jet to which the throttle slide is. Maybe I shouldn't read too much into the fact that fuel is rising up the tube, when a hand is placed over it (I assume with the engine cranked over), and when taking the bumpf literally. Probably, high air flow conditions usually lead to a depression over the power jet, where under lower air flow conditions the power jet is kept in a localised higher pressure region? Basically, placing an obstruction at the entry to carb is not what is normally meant to happen!
Is the float chamber vent clear?
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Cheers Steve H and Propellor for taking time.
Its brand new, spec built, so i doubt it would be blocked. You never know though so I'll have a look tomorrow.
Im a very simple mechanic and its struck me. I'm at a point with this build that i'm thinking to take it to a garage or someplace to give it a professional going over to get it started.
Mackenzie
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Is the carb the only thing to be changed since it last ran?
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Yep just the carb, that's why I'm pretty stumped
Mackenzie
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Yep just the carb, that's why I'm pretty stumped
Mackenzie
How about bolting the old carb on? If she runs then we know 100% that the issue is with the new carb set up. From there we can try to knock down the obstacles one by one.
If she doesn't start then the possibilities get more complicated, but at least we know.
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How d,ya know it,s a "she" propellor ? (Bike I mean) Sorry mac kenziebm can,t really help out with your carb problem, however I like the cool little bike oh and the flower bed looks delightful in full bloom.
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How d,ya know it,s a "she" propellor ? (Bike I mean).....
Quote mackenzie: "so today I decided to get her running right and she just would not start."
:D
I rest my case.
::) ;D
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DOH, there,s always one smart aleccy kid in the class eh. Still think the flowers look nice
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Yes, looks like mid summer.
Back to carb. Couldn't be an air lock in the fuel feed pipe could it? There is a section which goes up and over, especially when on the side stand. Mind you, that doesn't explain how fuel got into the bowl! Still looks a bit dodgy though.
You can't keep it going under any circumstances?
Edit: another little thought. If there are no dedicated idle passageways then covering the inlet will prevent any air at all from entering. Can't even get down the idle air passage, cause there ain't one! Dunno. Just throwing ideas around.
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Hey guys,
Sorry for the late reply, been doing a lot of overtime / the bike gives me the ump / its cold out there without a garage!.
I dont have the old carb anymore i sold it thinking i wouldnt need it if buying a spec made carb .. . Was told it should bolt on with no / very little fettering. Ive been reading non stop on Lectron carb tuning and setting up as well as general carb research. Still nothing conclusive or untried.
Its been so long with this bike with long periods of inactivity between, i think my little knowledge and patients has run a little dry with this project. I Think i will bite the bullet and just hand over the bike to a local dyno tuner and ask him to get it running nicely. If he cant do anything - put a match down the bloody petrol tank!!
Also ive bought a dirt cheap GN250 that has slightly taken over. Ill post some pics on a new build thread when i get it rolling at least.
I know one project at a time .. . But who listens to that when your on eBay?!
Mackenzie
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erm....I'm no great mechanic, but the thing that strikes me about your set up is that you have a hell of a long inlet manifold from the carb to the head and it's curved and a big bore...surely it'll take a lot of 'suck' from the engine to draw the mixture through? Considering that the original GN carb bolts straight onto the head ( pretty much) ? Just a thought. :-\
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I dont think the manifold should be a problem, just look at harleys inlet manifold and some customs, theyre at some right funny angles and lengths. The little single even has more compression then a harley cylinder so it should draw breath ok, it did 125+ miles on its first and only ride.
I had to have some kind of fabricated manifold becauseof the positioning of the transported engine, the carb inlet is very high to the frame
Mackenzie