23 replies to this topic

[mattj99]

Hope someone can help me out with this one.

 

After sitting for about a month I'm having some trouble getting my engine running. It'll run only with full choke and even then it runs roughly, sort of stuttering. It never gets to a point where its warmed up and I can lower the revs.

 

I reset the mixture nut to 2 full turns down (12 flats) to start with and kept enriching but makes no difference. With the jet fully down it'll run at 3000/4000 revs and higher if you touch the throttle but if you move the choke in it'll die straight away. 

 

It's a 998 with a hs4 carb

 

Fuel flow is good and the float bowl is about 3/4 full when I check.

 

I've taken the carb off and given it a clean, replaced the jet and the float needle - the float is set to the height in my haynes. Renewed the gaskets when I put it back on. Using SU dashpot oil and the piston drops nicely

 

I've replaced the plugs, leads and distributor cap, new vaccum advance tube and ends.

 

The timing was set at around 6 degrees BTDC using a strobe gun in October when it was serviced, I've checked it statically now and it still seems right. The valve clearances were done at the same time.

 

I'm at a bit of a loss where to check next, can someone suggest anything?

[MiniMadRacer]

Dodgy / contaminated fuel maybe

[MiniMadRacer]

or a blocked carb jet... try blowing down the jet with  piece of rubber tube.. might dislodge some debris

[mattj99]

Dodgy / contaminated fuel maybe

 

That's an idea, I bet the fuel has been in there since beginning of December. That's worth a try.

[mattj99]

or a blocked carb jet... try blowing down the jet with  piece of rubber tube.. might dislodge some debris

 

I've replaced the jet when cleaning the carb.

[MiniMadRacer]

When I drain old fuel out of my tank, I keep it and use it my lawnmower... just store it properly...do you have a fuel filter fitted... debris tends to float around the tank

[mattj99]

Yeah I've got one right before the carb.

[absx2]

If it`s a City E or HLE motor with a 10.3:1 compression ratio it could just be that the fuel has gone off.

I have personally had this problem in the past due to the supermarket 90 RON fuel going stale after a short time.

Yes I know I should use a higher octane but I'm a tight arse 

[MiniMadRacer]

I use std fuel, I have a heady 998 cc bog standard 35 BHP if I am lucky motor and I don't spoil it with exotic brews..runs fine

[mattj99]

It's actually half a tank of Morrisons in there and with this lockdown it's just not getting used. I'll get it drained tomorrow and treat her to some supreme or similar. Fingers crossed that'll be it.

If it`s a City E or HLE motor with a 10.3:1 compression ratio it could just be that the fuel has gone off.
I have personally had this problem in the past due to the supermarket 90 RON fuel going stale after a short time.
Yes I know I should use a higher octane but I'm a tight arse

[cal844]

Just let it sit without touching the throttle, I bet after a few minutes it'll take a rev and you'll be able to get the Choke in a bit

[mattj99]

Just let it sit without touching the throttle, I bet after a few minutes it'll take a rev and you'll be able to get the Choke in a bit

I did that yesterday, left it cloth pegged for a good 10 minutes 👍

[cal844]

Just let it sit without touching the throttle, I bet after a few minutes it'll take a rev and you'll be able to get the Choke in a bit

I did that yesterday, left it cloth pegged for a good 10 minutes 👍

Very strange, have you tried from the jet back to the float bowl with air to make sure theres no crud there? It sounds like that may be what's causing it. When was the air filter last checked?

[mattj99]

Just let it sit without touching the throttle, I bet after a few minutes it'll take a rev and you'll be able to get the Choke in a bit

I did that yesterday, left it cloth pegged for a good 10 minutes 👍

Very strange, have you tried from the jet back to the float bowl with air to make sure theres no crud there? It sounds like that may be what's causing it. When was the air filter last checked?

The air filter was replaced in October but with the filter removed it's the same. The jet seemed clear when I took the carb of to check but I replaced it with a new one from a rebuild kit anyway.

I think I'll try the draining the tank tomorrow and starting with fresh fuel.

[cal844]

That would be my first place to start