6 replies to this topic

[kaise7]

I have one of these on a 1330 cc, stage 2 head, needle BDL (was BFY), ignition timing near enough, good healthy spark, good coil,firing order in order etc. Engine is healthy, excellent high compression. However, I am having a continuing difficult time with spark plugs sooting up and what im assuming is overheating them to the point of destruction even though the engine temp stays within range. There are no obviously bangs, whirrs, hissing or sparking. The carb is my prime suspect and Ive been looking at a service manual i sourced through this forum. However, in the manual I have sourced it talks about two things that my carb does not seem to have. One is the piston lifting pin or an external button to test/lift the piston, the other is the fast idle screw. My carb only seems to have two adjustments, the jet screw (jet is flush with the bridge,yes it will go lower) and a screw pushing the accelerator cam down or throttle adjustment which I am/was assuming doubles for fast idle ? Hope this makes sense. Ive serviced the carb everything seems to be doing what it should smoothly but i seem unable to shake this (or at least what i think is a poor fuel / air mix) Im totally stumped !

[jaydee]

Are you using the correct grade plugs (champion N9Y or NGK BP6ES)?
Was mixture set up correctly?
The lifting pin, if you have one, is on the carb body just under the dashpot.

[kaise7]

jaydee im using N9Y plugs which seem to fare better than others. i just found that the main fuel line into the carb was tie-wrapped to a knackered steady ! Im sort of wondering if this has been frothing up the fuel on its way into the carb !!!

[kaise7]

forget that last observation,it was actually an/the overflow pipe !

[Neildanks]

The mixture screw is at the rear vof carb by your overflow pipe outlet may need adjusting

[petehuws]

From looking for the lifting pin I assume you want to check the mixture, what colour sooting do you have on the exhaust?
Jaydee is correct in that the lifting pin is built in, you'll need to.. Remove the air filter, put your finger into the air inlet elbow of the carb and slightly lift the chamber that's immediately infront. You want the rpm to rise slightly then immediately fall back when the chamber falls, if the rpm increases & runs away then your mixture is too rich, if it stumbles & falls then its too weak, from your description I'd err on the side of it being too rich. The HIF44 is Pretty good though at exhausting any excess, is your exhaust tip very hot at normal running? & have you the right coil ballast vs non ballast? Not sure what else it can be if your timing is spot on?

[kaise7]

From looking for the lifting pin I assume you want to check the mixture, what colour sooting do you have on the exhaust?
Jaydee is correct in that the lifting pin is built in, you'll need to.. Remove the air filter, put your finger into the air inlet elbow of the carb and slightly lift the chamber that's immediately infront. You want the rpm to rise slightly then immediately fall back when the chamber falls, if the rpm increases & runs away then your mixture is too rich, if it stumbles & falls then its too weak, from your description I'd err on the side of it being too rich. The HIF44 is Pretty good though at exhausting any excess, is your exhaust tip very hot at normal running? & have you the right coil ballast vs non ballast? Not sure what else it can be if your timing is spot on?

sooting is grey/black very dry not oily. do you mean lift the piston when you say chamber ? if its too rich which i think it will be, is the mixture screw the same as the jet adjustment ?, the carb only seems to have two adjustments ! by exhaust tip (if you mean the tail pipe is not overly hot its a RC40 exhaust system). i have a sports coil and im getting a strong spark cold at least, becomes less reliable as engine is run, what coil should i have ?