9 replies to this topic

[Diag]

Hi all,

Hope I am posting in the right place.

I have an odd issue with twin HS4's. The fuel level is too low. These are the plastic floats so only adjustable with washers under the seat/valve.

I replaced the valves with the new type mini spares ones. Using the thinnest washers the level is still too low. Its as though the valve is too long. The old ones were another design, not the nylon removable needle type, but are the usable. The old and new measure the same.

Looking at the fuel level in the jet it looks to be about 2mm lower than it should be.

Has anyone come across this? I am wondering if the old design are shorter? Maybe someone has previously changed the float bowl covers or the float type.

Any thoughts welcome.

[Spider]

You can try fitting the seat up with no washer they will usually seal but if it doesn't, a dab of the right Loctite will soon cure any leak.

 

Check what level you've ended up with first.

[luismx123]

Hi all,

Hope I am posting in the right place.

I have an odd issue with twin HS4's. The fuel level is too low. These are the plastic floats so only adjustable with washers under the seat/valve.

I replaced the valves with the new type mini spares ones. Using the thinnest washers the level is still too low. Its as though the valve is too long. The old ones were another design, not the nylon removable needle type, but are the usable. The old and new measure the same.

Looking at the fuel level in the jet it looks to be about 2mm lower than it should be.

Has anyone come across this? I am wondering if the old design are shorter? Maybe someone has previously changed the float bowl covers or the float type.

Any thoughts welcome.

I did just this on my single hs4 over the weekend. I first had a single plastic washer, realised the float was sitting to low? I.e closing the value too soon, so I removed the plastic washer and that made the distance better (similar to the original)...

I have however since had issues with fueling. Happened around 5 times tonight driving for 15km. Random engine cutout, gas smell, need to crank the key over a few seconds to probably fill the float chamber again and then the car started. No idea whats causing that...As if it would be getting stuck and not letting any fuel in... i dont know...AND when I pull the choke, the engine doesnt rev up but drops rpm and sputters bad....

Hope someone can help you/me :/

[Spider]

I did just this on my single hs4 over the weekend. I first had a single plastic washer, realised the float was sitting to low? I.e closing the value too soon, so I removed the plastic washer and that made the distance better (similar to the original)...

I have however since had issues with fueling. Happened around 5 times tonight driving for 15km. Random engine cutout, gas smell, need to crank the key over a few seconds to probably fill the float chamber again and then the car started. No idea whats causing that...As if it would be getting stuck and not letting any fuel in... i dont know...AND when I pull the choke, the engine doesnt rev up but drops rpm and sputters bad....

Hope someone can help you/me :/

 

 

I think you may have a leaky fuel pump.

[luismx123]

 

I did just this on my single hs4 over the weekend. I first had a single plastic washer, realised the float was sitting to low? I.e closing the value too soon, so I removed the plastic washer and that made the distance better (similar to the original)...

I have however since had issues with fueling. Happened around 5 times tonight driving for 15km. Random engine cutout, gas smell, need to crank the key over a few seconds to probably fill the float chamber again and then the car started. No idea whats causing that...As if it would be getting stuck and not letting any fuel in... i dont know...AND when I pull the choke, the engine doesnt rev up but drops rpm and sputters bad....

Hope someone can help you/me :/

 

 

I think you may have a leaky fuel pump.

 

really?

out of the blue?
Its weird. I happened last night too. MY gf drives this morning, same 15km, nothing... I get in, it dies... Was thinking of swapping in the old float valve again to see if that remidies the issue but no idea...

[Spider]

I say the fuel pump based on that you can smell the fuel, so must be coming out somewhere and yet the fuel bowl is low or empty.

 

Might also be a cracked fuel hose.

[luismx123]

I say the fuel pump based on that you can smell the fuel, so must be coming out somewhere and yet the fuel bowl is low or empty.

Might also be a cracked fuel hose.

So I did some tests today. Some on purpose.

Some not so...


It is 100% the overflow from the float chamber. there is no one on the road today so as soon as it concked out I pulled over to check where the fuel came from. Saw it dropping from the end of the overflow pipe. So that confirmed that nothing else was the problem. I then swapped back the old needle which used to give me issues. Went for a drive, carb overflowed again and had to do a roadside fixeroo. Turned the old needle around (90° or so) and since then it's been fine. I'll give minispares a call and ask if they have a troubleshoot for this issue/if they are aware that their replacements have some sticking problems. I guess I'll buy a new float needle from SU directly with the newer type tips. Let's see....

[Diag]

If you or anyone else has an old type needle and seat could you measure with a vernier from the sealing base of the valve to the outer end of the needle while in the close position? 

 

The one I have has new valves only a short time ago and they were sticking. The old type did give trouble with wear but when replaced on a good clean system they lasted a reasonable time. Not sure I would trust the later type even if I didn't doubt they are not the correct length.  

[luismx123]

If you or anyone else has an old type needle and seat could you measure with a vernier from the sealing base of the valve to the outer end of the needle while in the close position? 

 

The one I have has new valves only a short time ago and they were sticking. The old type did give trouble with wear but when replaced on a good clean system they lasted a reasonable time. Not sure I would trust the later type even if I didn't doubt they are not the correct length.  

i removed the "uprated minispares version" as it was only giving me trouble. Will order new "old type" needles. just swap the older types back in and be done with the new ones

[Spider]

 

I say the fuel pump based on that you can smell the fuel, so must be coming out somewhere and yet the fuel bowl is low or empty.

Might also be a cracked fuel hose.

So I did some tests today. Some on purpose.

Some not so...


It is 100% the overflow from the float chamber. there is no one on the road today so as soon as it concked out I pulled over to check where the fuel came from. Saw it dropping from the end of the overflow pipe. So that confirmed that nothing else was the problem. I then swapped back the old needle which used to give me issues. Went for a drive, carb overflowed again and had to do a roadside fixeroo. Turned the old needle around (90° or so) and since then it's been fine. I'll give minispares a call and ask if they have a troubleshoot for this issue/if they are aware that their replacements have some sticking problems. I guess I'll buy a new float needle from SU directly with the newer type tips. Let's see....

 

 

OK, so previously when you've checked the float bowl, it was not empty ? Sorry, I thought that's what I read in your first post on this.

 

It's likely the needle and seat, but could also be a bent pin that the float swings off and / or a worn float. Both of these can cause the float to jam and not let the needle seal off.

 

Also, check the fuel pressure at the carb.