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MG Midget and Sprite Technical - Carb Jets

Any comments on any differences between the standard jets (part no 27) and the waxstats (part no 28)

The original jet on the front carb requires replacing so will change both, but are the waxstats worth twice the price or are the standard jets an adequate replacement on HS4 SU carbs on a 1500?

Thanks
Tim

Tim Lynam

Without recalling why - it was 20 years ago, - I was persuaded by the arguments, to do away with the waxstat jets on my 1500 and replace with standard ones.
Someone with better memory than I will no doubt elaborate
GuyW

Tim,
I recently got an email from MGOC saying they were doing a kit to replace the waxstats but I can't find it on their website so you'd have to ring them for info. 01954 230928


Nigel Atkins

I thought everyone ditched the waxstat jets as it's just another Heath Robinson bit of BL bodgery to go wrong!

Did you get to the bottom of your issues Tim, was it just the jets?!

Malc.
Malcolm

Tim, don't use the waxstats they were an attempt by BL to reduce emissions, the theory being is if the air temp is high and therefore less dense you need less fuel. As stated MGOC in this months Enjoying MG are offering a kit to replace the waxstats with non waxstat jets for £69.95.

If you were having issues with, say, leaking fuel pipes on your jets this might be a reasonable option. If not and you just want to get rid of the waxstats you can do a "4p converstion". This involves removing the waxstat capsules and replacing each with two 1p coins, they are a perfect fit.

Bob
R.A Davis

Thanks to all for the comments, looks like its not worth paying double for the waxstat jets.

Malc, not sure if its just the jets that were causing the issue at Curborough but its the first thing to change as one is totally knackered, after a frustrating day not had the will to get back under the bonnet.
Tim Lynam

Bob,
out of interest have you got details and photos of the 4p conversion you could put up?
Nigel Atkins

Nigel, how about this

http://www.dunlopclassics.co.uk/waxstats.htm
R.A Davis

Thanks. Looks pretty straight forward.
Nigel Atkins

"The Wastat was designed with the intention of thermostatically making minor changes to the fuel/air mixture. There are more than a handful of anecdotal complaints that the thermostatic cartridge actually causes more mixture problems than justify its use for reduced emissions. That is why there is information on the web both about the 2-penny jet conversion and the fixed jet conversion parts."

Waxstat jests are a service item it seems.

"When the wax hardens with age they fail to give a consistent mixture."
anamnesis

Isn't this another example of why you should "keep it simple"?
Bill Bretherton

Bill, maybe a good job the motor manufacturers did progress and did not keep everything simple or else we would still have been adjusting points and carbs on our modern cars, but regarding the waxstats, looks like your right!

I decided to go for the conversion kit on the new jets after a long conversation with the producers of the SU spares Burlen Fuel Systems at Salisbury and what a great change to speak to a technical department that is helpful and not wanting to fob you off and safe in the knowledge that the parts are produced in the UK and not in some Chinese factory producing parts that will probably fail in a few days or weeks.

The parts look real good quality, well packaged but not cheap, but if they do the job and don't fail then well worthwhile.
Their Parts & Specification catalogue is also excellent and easy to follow and much easier than many online parts breakdowns.
Tim Lynam

Isn't there something similar in the hif carbs?

Although that's bi-metal, I wonder if that too becomes error prone with age.
anamnesis

Tim,
I'm glad you have it sorted and that you found someone decent to talk to at SU, if they see your post he will though probably get reprimanded for going against company policy.

I can't agree that their website is any better than most, their listings are very idiosyncratic and search facility sometimes wouldn't even turn up their own part numbers given on other pages.

Good to hear you got good service and well made parts.
Nigel Atkins

anam,
this(?), from SU site although I couldn't find the "more detail in the relevant literature" on a quick look of the SU site.

http://sucarb.co.uk/technical-hif-type-carburetter-emission-control-features


Nigel Atkins

Yep that's it Nigel. I wonder how well/accurately it works now it's decades old.
anamnesis

Not an MG but my Dolomite 1850 had waxstat jets on twin HS4 carbs and when I rebuilt the engine I didn't think anything about getting rid of them. What a mistake! Once on the road the car ran beautifully until the engine was thoroughly warmed up, say 3 or 4 miles. Then it started to lose power. Going along the local bypass at around 60 mph the speed gradually went down until it would only manage 35 mph on full throttle.

I took one of the waxstat capsules out and watched it while I heated it with a hot air gun. It expanded by at least 1/4 inch, which meant it pushed the jet up by the same amount. This weakened the mixture so much that the engine was starved of fuel at anything above a light throttle application.

I bought standard jets from Burlen and once fitted and tuned the car was revitalised and has performed well for over 3000 miles now.

Waxstats - chuck them away!
Mike Howlett

This thread was discussed between 06/07/2022 and 12/07/2022

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