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Hs4 Carb Adjusting Nut


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#1 maccers

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Posted 26 January 2022 - 08:32 PM

Hi all, 998cc having some running problems that suspect is carb. All electrics are new and correct parts for dizzy, gap set on the points. 

 

Feels like car really bogs down under load, I went to change the mixture but it seems to do very little. The air box is on and filter fitted, but when I turn the adjuster either way nothing happens, I have moved it maybe 4 full turns in either direction and at idle the engine speed does not increase or decrease, nor on the road does it seem to have made much difference.

 

I assume that is supposed to move something up or down, is there any way to see this while fitted to the car? 



#2 sonscar

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Posted 26 January 2022 - 09:54 PM

The jet bears on the nut and should move with it.Pull the choke and look at the jet,it should move 10mm down and should return fully with choke off.Slim chance but you are moving the correct nut?the lower of the two.The top nut secures the jet bearing.Steve..

#3 maccers

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Posted 27 January 2022 - 06:24 AM

The jet bears on the nut and should move with it.Pull the choke and look at the jet,it should move 10mm down and should return fully with choke off.Slim chance but you are moving the correct nut?the lower of the two.The top nut secures the jet bearing.Steve..

 

I'll look in better light today, I am sure it was the very lower nut near the bottom of the assembly, had a red plastic cap on the last part before I burn my hands on exhaust :-)



#4 sonscar

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Posted 27 January 2022 - 09:56 AM

Red plastic cap could indicate a waxstat replacement jet,these are tricky to get to move smoothly without the linkage sticking.Steve..

#5 Chris1275gt

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Posted 27 January 2022 - 10:04 AM

Sounds like you need an su tuning tips book and a colour tune plug. If you learn how it works it makes it much easier to know what’s wrong and perhaps it needs an overhaul and refurb kit which is relatively easy to do.

https://www.ebay.co....375#UserReviews

The colortune plugs seem not easy to get hold of at the moment so if you wish to borrow mine pm me and for the postage cost you can use it and return it through the post. I’m in Woolley Reading Berks if your anywhere near, you can pickup the book as well.

Edited by Chris1275gt, 27 January 2022 - 10:06 AM.


#6 maccers

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Posted 27 January 2022 - 10:05 AM

Red plastic cap could indicate a waxstat replacement jet,these are tricky to get to move smoothly without the linkage sticking.Steve..

Its been sitting since 2017 - I cleaned out all fuel parts (mech pump, tank, metal lines) and replaced rubber hoses, inline filter and done lots of carb cleaning but have not removed it and fully stripped. Might need that...



#7 maccers

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Posted 27 January 2022 - 01:53 PM

So the jet was really stuck, the choke cable did not do anything, I could not get the cam to budge at the carb end. Took carb off, the small pipe between the fuel pot and the jet was very brittle and was snapped. The actual jet was also jammed in the brass guide, it was almost glued in, I guess thats what leaving a carb to sit in fuel for 5 years does!

 

New bits on order. 



#8 Tornado99

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Posted 27 January 2022 - 06:21 PM

So the jet was really stuck, the choke cable did not do anything, I could not get the cam to budge at the carb end. Took carb off, the small pipe between the fuel pot and the jet was very brittle and was snapped. The actual jet was also jammed in the brass guide, it was almost glued in, I guess thats what leaving a carb to sit in fuel for 5 years does!

New bits on order.


Yes the fuel feed line to jet likely has rubber liner that can't handle long. Term exposure to modern fuels, making it brittle.

Would also recommend replacing the parts within the float bowl as good measure.

#9 maccers

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Posted 28 January 2022 - 08:50 PM

Sounds like you need an su tuning tips book and a colour tune plug. If you learn how it works it makes it much easier to know what’s wrong and perhaps it needs an overhaul and refurb kit which is relatively easy to do.

https://www.ebay.co....375#UserReviews

The colortune plugs seem not easy to get hold of at the moment so if you wish to borrow mine pm me and for the postage cost you can use it and return it through the post. I’m in Woolley Reading Berks if your anywhere near, you can pickup the book as well.

Thanks Chris, hugely appreciated, I’m in Surrey but often work at Reading Int Business Park. I actually found the jet is needing replacing so hopefully this will get it running good. I live close to VMAX Scart who tunes my own 1293 s/c on the rollers, I should be able to literally coast it there if it needs setting up. Thanks for the offer though :-)



#10 Steam

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Posted 28 January 2022 - 10:08 PM

As well as draining the tank completely, blow ALL the fuel lines through to get rid of the old fuel.

Valves and guides do not like old fuel at all.






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