11 replies to this topic

[jakejakejake1]

Car: 1991, 998, HS4 with waxstat and overrun valve

Hi everyone,

My car was idling really bad the other day, and I had to keep it about 1200 rpm or it would stall.
Then my friends got in the car and I was explaining to him about the choke as he had never seen one before.
After pulling it all the way out and pushing it back in again the car would not start.
So I went through the things I thought it could be, long story short after taking the dashpot off it was evident that the jet was stuck about 10mm below the bridge.

I immidiately realised this was wrong and push the jet back up, but whenever the choke is pulled enough to move the jet, the jet sticks and doesn't return.

I'm guessing the jet is bent or something, and this is causing it to stick. I tried a dab of oil and pushing/ pulling the jet a bit in an attempt to loosen it but to no success.

So my question is, what rebuild kit should I go for, and would this also cure the stalling when revs drop?
Because I would imagine as long the the choke doesn't move the jet, and the jet is in the correct position, the car should be fine once going which is what is confusing me.

Link to rebuild kit:http://www.minispeed...n-throttle-disc
I think it would be for the best to convert to non-waxstat and a plain disk, is this kit all I need to achieve this?

Thanks, Jake

[jaydee]

The jet holders are different IIRC, easier/cheaper to get a waxstat type refurb kit and replace the waxstat with a coupe of 2p coins.

[jakejakejake1]

So I could get this one to fix the jet problem: http://www.minispeed...hs4-waxstat-jet

Or this one to also replace the butterfly: http://www.minispeed...hs4-waxstat-jet

And convert either by replacing the waxstat piece with two pennys?

Do you need any special tools to fit either kit, as I heard about having to ream something out to fit it, would this be the throttle spindle bushings?

I'm just trying to figure out if its worth paying the extra for the full kit if I won't be able to fit the new shaft and bushings...

[dklawson]

Unless the jet has hit the bulkhead it should not be bent. Before spending any money on a rebuild kit, remove the jet completely and inspect it. If it is bent the bend will be apparent. If you cannot see the bend itself you may see witness marks where the jet has been rubbing. You can straighten the jet if it is not too bad. You can also dress those high (rubbed) spots down on the jet diameter using a file. However, you may not find any damage at all. You may find something as mundane as a stuck linkage or a broken return spring. Check all this out first before buying parts you may not need.

[jakejakejake1]

That's a good point, although when looking at the jet from the side, it does look like its bent slightly towards the engine where the metal tube bit attaches to the bottom part, but as I never look at it much before I don't know if this is usual or not. But I will whip it off and take a look anyway.

Cheers

[dklawson]

Do not worry about how the expansion capsule casting appears relative to the carb body. What is important is how straight the brass jet is. The brass tube is the only part that moves in and out of the jet nut/bushing so it is the part that needs to be straight. With care, a mildly bent jet can be straightened and its outside diameter can be cleaned up to move smoothly again. It does involve some time, dry fitting of parts, and with all jet changes... re-tuning is likely to be necessary when you are done.

[jakejakejake1]

Well i got the jet off, and as expected its well and truely bent. Near the bottom of the brass pipe and by a large amount. A good 10 degrees or so, this is causing the outer brass bit to bind if the inner is within about 10mm of the top.
As i am having trouble bending the inner tube straight again, could i widen the bottom of the outer brass part to increase clearance? Or is this a no-no?

Cheers

[jimnali]

The jet is probably worn anyway so throw it away and buy a new one.

[dklawson]

^{Agreed. Wth a bend that bad I would order the replacment jet and re-tune the car. However, make sure you look at the situation carefully before saying that the job is done. Try and determine if the engine mounts/steadies are loose or worn or what else may have allowed the jet to be struck and bent in the first place.}

[jakejakejake1]

Well my engine steady snapped the other day haha, followed by limping home, where I had to keep the idle over 2000rpm or the car would stall. I'm guessing this is when it happened haha been having a few running problems since then and couldn't pin them on anything in particular.

And the bend actually straightened out ok in the end, and after a bit of filing to smooth it off it now moves freely. So will finish putting it back on tomorrow and see how things go, if it doesn't work it doesn't work and I will have to order a new jet anyway. So I haven't really lost anything in trying :)

Thanks for the help

[dklawson]

Excellent and you are absolutely correct ! All you have invested at this point is some time and you may find the repaired jet works fine indefinitely. Oh... do get the steadies fixed!

[jakejakejake1]

Yeah the steady was fixed asap after it broke, and so far after refitting the jet all seems to be ok, granted I haven't driven the car much but in the short time I did put it through its paces and tried with/ without choke and all seems to be working good, just a case of finding the right mixture now haha. Also while it was out I swapped the waxstat for two pennys, so hopefully it will last me a while before any other problems occur :)