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Seeking HIF4 gurus - need help!

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I put in the new float valves and like magic no more leaking. Also adjusted the floats while in there.

I was able to lean them out a few turns, will see how it drives tomorrow!
 
Rick, Hope you can read these. You might already know this, but I thought I'd give you a little more info on your carbs. PJ

carbsetup1.jpg
 
Thanks Paul, yes looking at the book I did get all that sorted out. Now it would seem I've got a bad vacuum leak as I can't get it to idle below about 2000 rpm with the carbs leaned properly. Going to be looking at that again after the long weekend.
 
After reading all of this I am beginning to agree with Paul that the vacuum leak is not so necessarily at the throttle shafts but at a vacuum take-off or some such.
It may be interesting to first plug all of the takeoffs that aren't plugged yet and see what happens.
BillM
 
Thanks Bill, I'll look for that when I get back home.
 
...and Rick, if you are missing your 10mm socket I think that I have it.
BillM
 
Heh - that's where it is...

Thanks Bill, if wither of us remember next time we get together...

I think I've still got a few things of yours too.
 
Paul161...That is one beautiful engine room.Shows very well how the plumbing should be run with the HIF's. A thing of beauty!
 
I sprayed starting fluid at everything yesterday and could find no vacuum leaks anywhere.

Now I suspect the throttle discs, will pull the carbs and look at them next.
 
The throttle disc on the front carb was not closing.

Since the other one had the poppit removed and soldered we did it to this one as well.

Made sure both discs were centered, reattached and tuned carbs and WaHoo it runs great now!!!

Thanks again to BillM - skilled, knowledgeable and an all around great friend!!!
 
The throttle disc are angled on the edges, and thay only seal in one direction, so they could be on upsidedown, if so they will not seal. Also HIF4s are unique in that their butterfly orientation is opposite for the HS4s, meaning if you looking at the carb right side up from the rear at the butterflies, the upper section of the butterfly is closest to the back of the carb, and the lower section angled inward, this is opposite from HS2, HS4 and the other HS series carbs.

Here's a tip that worked for me, when I first starting rebuilding carbs that may help you next time, take one apart at a time, then atleast you have the other one to look at for a reference.
 
Thanks Hap - yes that's the way my discs were installed.

Now for the ongoing saga...

I noticed it was struggling above 3500 rpm going uphill (up I-90 between Issaquah & Snoqualmie). It did this again this morning going down hill as well. Just kind of struggles above 3500 - 3800 rpm.

Also after turning off the engine a few seconds go by then "bang" I get a detonation back around the muffler. This only happens after I've been on the road more than 15 minutes, generally driving highway speed.

I will double check my timing tonight after work - what else could this be?
 
Excess fuel building up in the exhaust system. P'raps the floats are a bit too high or the pump output pressure is beyond the float needle's ability to shut off.
 
Thanks Doc - I set the floats according to John Twist's instructional video.
Pump is a low output one and I also put a regulator in just to be sure.

Not saying the pump or the regulator are doing their job or that I didn't make any mistakes.

Could it be the needles & jets being old & worn?
I know, just throwing money at it, but if that's it then I'd have to get to it some time anyway.
 
It ~could~ be but if float height and pressure are right, fuel can't get in there easily. Are you relying on one of those poxy dial-type regulators? Put a real gauge on the line at the carb to TEST whether it really is lower than 3 PSI.

When you had the pistons out did you pay attention to the jet orifice shape? It is usually noticeably worn to oval shape before odd stuff starts happening.


...and by-the-by we're talkin' here about English carbs on a Japanese motor...

:jester: :devilgrin: May need to introduce some anti-rejection drugs. :devilgrin: :jester:
 
:laugh:

Yes - I see your point there Doc.

I did not look closely at the shape of the jets - but that's easy enough to do.
I'll get out my +2.5 reading glasses and take a look in there!!

Don't have a real gauge for the fuel, yes it is one of those dial type regs.
 
They restrict volume, pressure is a whole diff'rent animal. That may be your 3500 RPM stumble issue.

You could get a cheap pressure gauge from parts stores, Harbor Freight or NAPA. 0-20 PSI would work fine.

What pump is it you have on there?
 
I think it's a small facet pump, don't know the part no. off hand.
Thanks Doc, good idea.
 
They make a few different types. The one we found to work well is a steel cased cube with a power transistor mounted to it, specifically designated low pressure. I've since switched to a Carter #P60504 for cars with Weber DCOE's. They're just as sensitive to over-pressure as the SU's . No issues so-far.
 
Ok, well I got this one from BillM.
It's a metal cube type, don't know if it has a transistor mounted on it but that's easy enough to check. It may even have the psi rating written on it, I will look for that and a part number.
 
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