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Fuel Evaporation?

N

NickHay

Enthusiast
Messages
39
Location
High Wycombe
I've finally got the old girl running to a point where we can go more than a mile but my issue now is that when hot it seems to idle okay but when trying to actually drive it the engine cuts outs.
When it finally starts again there is lots of coughing, spluttering , popping and smoke. My immediate thought is fuel evaporation but the carb already appears to have a spacer on it.
Has anyone else encountered this and managed to get round the issue?
 
I had a similar problem and broke down, so had to clean out my carburettor/jets and then drain/remove the fuel tank and clean it out. I also fitted longer studs on my carburettor manifold with two spacers which helped with fuel evaporation problems during the hot summer months.20250315_064746.jpg
 
Last edited:
Cyprusnoddycar said:
I had a similar problem and broke down, so had to clean out my carburettor/jets and then drain/remove the fuel tank and clean it out. I also fitted longer studs on my carburettor manifold with two spacers which helped with fuel evaporation problems during the hot summer months.
Click to expand...
Yes apart from fitting the longer studs I've done everything else. I'll give it a go, cheers
 
Could be solution to my hot start problems i have during summer.

You use standard air filter housing? It is not touching bonnet?

Do you keep that arrangement thru all year or you switch back to standard during winter?
 
Check for clogged main jet and / or fuel filter, if one is fitted.
 
I have the same problem. Fitted an heatshield between the manifold and the carb, less problems on hot start, but not solve the problem.

I will try change the fuel filter to another location.

PXL_20250314_084243051.jpg
 
You only have a thin paper gasket on your carburettor manifold. See my photo above with X2 thick spacers fitted.
 
I found that it was the new petrol E10. I rerouted the pipe from the fuel pump as it passed over the engine and I also try to only use the old petrol.
 
Hi, not sure what you mean by "the old petrol ", but if you use higher octane E5 you shouldn't have any problems. If you also use an anti ethanol product, for example Millers Oils one, which also has an octane booster, your engine should run smoothly. Some R4 engines suffer from fuel evaporation when hot, which makes them tricky to start, but once started they run fine. Mine does this, and I've learned to live with it. Cranking with full throttle and it starts.
All the best Bry.
 
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