17 replies to this topic

[driftz]

Noticed my engine is bogging/cutting out when I do really hard cornering or fast tight circles. Float and needle/seat are new and set to factory specs. Fuel pump, lines, and filter are new as well, carb is tuned well and runs well otherwise. its not a super urgent problem but if i'm goofing off doing 3 wheel donuts, or tight 180 switchbacks its hampering my fun

 

Would a float bowl extender aid my problem?

[nicklouse]

Engine is a? And the spec is?

Fuel pump is?

Anything else in the fuel system?

[driftz]

Engine is a 1275 A+ MG metro unit. Intake/header/exhaust. Carb is a single HS4, BQ needle red spring, velocity stack, cone filter. Fuel pump is a brand new

 

http://www.minimania...990-Aftermarket

 

Nothing else in the fuel system, all new soft lines and new filter

Edited by driftz, 16 November 2016 - 11:52 PM.

[nicklouse]

Does it seem to be more to one corner than the other?

And was the car 998 before? That is to say not a factory 1275.

[driftz]

I believe its happened in both directions but I will have to try back to back circles to see if its better or worse in one direction.

The car was originally a 998 (its a 1975 Canadian spec car, 89 MG metro engine)

[nicklouse]

Ok it it is both sides then I would say it is an issue before the pump.

On thing of note is (I have heard) that 998 cars had a smaller ID on the metal fuel pipe front to back.

That is the first thing I would change. I would then back flush it to see if anything comes out and then section it in a few places to look at the condition.

While the tank is empty have a look inside so any thing that might be causing issues. Eg rust, deposits etc.

[driftz]

Ok thanks. I may try just replacing the hardline and going from there. Do you remember off hand what size it should be?

[Spider]

I'm not too sure it would be from the fuel line from the fuel tank, could be, but I think you'd notice the issue at other times, not just cornering and it would take a few seconds to become apparent.

 

But, to check if this is an issue, temporarily fit a Tee Piece in to the fuel line right where it connects to the fuel bowl and fit a pressure gauge (with about 4 feet of hose!) to that so you can hang the gauge inside somewhere where you can see it. Go for a blast and check the pressure when the problem sets in. You'll soon see.

 

I'd suggest checking the Jet is 100% clear of any muck. You'll really need to remove the carb to check this properly. I recall having this same issue but only on Right Handers (with a HS4) and that's what that was. It could also be that you are 'reaching' the limitation of what a HS4 (or any HS carb) can do and you might be better off going to a HIF44.

 

I doubt that fitting float bowl extensions will help as you can't raise the fuel level in the bowl (if set correctly) without to flooding over and flowing continuously through the Jet.

[Allrounder]

Had a similar issue during autotests with my 998. Put it down to fuel moving in the float bowl. Could try the hiff4. Sure that's what the others auto testers use. Since I've gone 1275 I run injection and never had the problem again.

[carbon]

As above, had this with mini marcos fitted with HS4 carb when tackling roundabouts at speed, it could go round corners very well

 

Same as Moke Spider, this was with sharp right hand turns only, and I put it down to fuel moving away from the jet and weakening off the mix.

[driftz]

That's what I figured it probably was. I'm wondering if its a limitation of the car, or a legitimate problem. If I were to do an autocross it would most definitely sputter on me, normal day to day driving, no problem.

 

When I had the carb apart not long ago I gave it a thorough cleaning, would be surprised if there was something gumming up the jet, but you never know.

 

I would prefer to fix the carb I have, paying out $$ for a new HIF to fix a simple problem If there is another solution seems like a waste

[panky]

I dont suppose there's enough room in the float chamber to fit a baffle near the fuel take-off?

[nicklouse]

Hence the question as to when it was happening.

If you are thinking it is a fuelling issue in the float chamber then you also have a fuel supply issue. A high capacity electric pump in the boot/rear and a filter King regulator and filter on the left of the carb.

We found this cured any feeling issues as the pump supplied fuel to the regulator all the time and then there was a good supply of fuel at a suitable pressure 2.5-3psi (note new needle valves and seats will take a higher pressure they say) also th fuel in the filter bowl also helps level out any flow issues. Fit a blanking plate where the pump would be.

[driftz]

*little update*

 

Was out doing some filming the other day in an industrial lot and had the same issue. It was very noticeable from going left and seemed totally fine when going right. Was stalling when going around fast left hand roundabouts after about 1 revolution. 

 

prior to this I have had the carb rebuilt and float level re checked, and it all checks out, very annoying. 

 

I am going to fit a pressure gauge and see if its loosing pressure on the line prior to the float, if so would a larger diameter line help or would I have to convert to a high flow electric pump (would prefer to retain my mechanical one)

[carbon]

Which side of the carb is your float chamber on? There are 'LH' and 'RH' versions of the HS4.

Edited by carbon, 15 June 2017 - 08:16 PM.