HR Carb issue

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al peckenpaugh
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HR Carb issue

Post by al peckenpaugh » Sun Aug 26, 2018 7:50 am

I've posted this issue in the other forums but I'm gonna try it here too, just in case. I have a couple HR's on my rear dual that I can't seem to make act right. I'm pretty sure it's a carburetion issue because I've pressure checked, timed, and even switched engines. Same result. THIS - On the stand - set idle mixture, idles fine. Hit throttle and it will bog until Hi speed needle is out enough to feed it. Revs fine but on decelerating, main nozzle still dribbles fuel enough to flood engine. Both carbs. Every different situation.
I've run pop offs from 14-20, raised and lowered the arm, disassembled and assembled countless times, replaced suspected leaky welch plugs, tried every combination of needle twisting, removed, cleaned, replaced and switched main jet nozzles, replaced every gasket and diaphram countless times and pulled out most of what I have left for hair. What am I missing?

Rob Voska
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Re: HR Carb issue

Post by Rob Voska » Sun Aug 26, 2018 8:28 am

After idling when you hit the throttle is it lean or loaded up with fuel?
Will it take throttle slowly but not all at once?
Gas or alky?
Reeds good and sealing or warped / chipped?
Fresh fuel?
Plugs fouled or clean?
Are both carbs the same number & drilled the same or have they been modified?
Check balls in high speed nozzles?

al peckenpaugh
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Re: HR Carb issue

Post by al peckenpaugh » Sun Aug 26, 2018 9:32 am

Thanks Rob, Good questions

1 After idling I can make it bog lean then turn out HS needle til it accelerates
2 Depend where I have HS needle. If open 1/2 a turn or so it will take it slowly - open more it will rev right up but then flood it on deceleration
3 Gas
4 Fresh reeds
5 Fresh fuel
6 New plug
7 OK.. Got me One is a 67A, one is a 95A Don't know if they're drilled the same but they act the same. I have a 63A on a 101 that works great. My dual has two 91's.
8 Check balls in high speed nozzles. I've taken them out and cleaned them. They seem to seal. What they don't do is seal after a WO throttle. As rpm's come down they're still pouring fuel. It's my understanding that atmospheric pressure has to close them after throttle plate is closed. It's just not happening. Throttle plate is closing as tight as I can get it and still get it to tick over at a very low idle.

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Kurt Bogerman
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Re: HR Carb issue

Post by Kurt Bogerman » Sun Aug 26, 2018 2:10 pm

Hi, Al.

I read your post and did some searches on the net. Lots of HR conversation on snowmobiling sites. I came across a thread where a guy was running lean. He eventually discovered that the inlet needle he had installed from an aftermarket kit was longer than the original inlet needle and was restricting flow. I wonder if you have the opposite problem. Also -and I'm no expert in this matter-, but there seems to be a lot of talk about pop-offs in the 10# range.

This is the link I found to be most informative, so far. Nice photos of reassembly process, too:

https://vintagesleds.com/bs/index.php/t ... 202.0.html


Just some ideas.... Experts, weigh in!

Kurt

al peckenpaugh
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Re: HR Carb issue

Post by al peckenpaugh » Sun Aug 26, 2018 7:18 pm

Thanks for the reply Kurt. Interesting read but doubt it's my needles and seats. They hold pressure and pop off properly. Those snowmobile guys are feeding a lot more engine than us so they probably need the lower pop off. The HR on my 101 is set at 16 and runs like a clock. The one thing I didn't do was replace the main ball nozzles. Took them out, cleaned them, and tested as best I could. A leaky nozzle would cause my issue I suppose. But this is my dual. Both nozzles leak? Maybe. I'm still thinking I did something dumb or overlooked something obvious....... I suppose I replace the nozzles and eliminate the possibility

Al Hasenfratz
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Re: HR Carb issue

Post by Al Hasenfratz » Mon Aug 27, 2018 12:23 am

What happens if you open the throttle plates/shutters a little more with the idle speed screw to cut some of the high vacuum produced when the throttle goes closed? It may not fix your problem but may help with the diagnostics. I am picturing what happens when you choke the carb by hand and pull a bunch of fuel out the nozzle. I think that happens too when we close the throttle before the corner, it gets a blast of fuel from the high side that helps it pull off the corner. Just some thoughts. Al

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Kurt Bogerman
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Re: HR Carb issue

Post by Kurt Bogerman » Mon Aug 27, 2018 8:51 am

Spitballing...

Do you have your spacer gasket between the carb body and the metering diaphragm, and not on the wrong side of the diaphragm?

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Kurt Bogerman
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Re: HR Carb issue

Post by Kurt Bogerman » Mon Aug 27, 2018 12:19 pm

https://tillotson.ie/kits-parts/illustr ... rts-lists/

The HR parts list on that web page shows some differences between your two carbs. Not saying that's related to making either engine run individually, but I wonder how the two will run together, once you get each of them going. The carbs have different low speed screws, for one example.

The exploded view in the document is nice, too, though.

Best of luck!

Kurt

al peckenpaugh
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Re: HR Carb issue

Post by al peckenpaugh » Mon Aug 27, 2018 12:48 pm

Thats pretty good detective work, Kurt. I'll have to look at that tonite.... What else did you find different? Thanks

al peckenpaugh
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Re: HR Carb issue

Post by al peckenpaugh » Mon Aug 27, 2018 6:51 pm

Kurt,
I looked at that parts list and I don't see different low speed screws. I have 4 HR carbs 63A, 67A,and 2-95A. They are all listed as "similar from the standpoint of metering systems being the same", in the Vintage Snowmobile crossover reference from Tillotson http://vintagesnow.com/Carburetors_file ... 20desc.pdf They all use 14321 for low speed and 14499 for high speed. My issue is the high speed side anyway I think.
Upon closing butterfly to idle position after wide open rev (decreasing vacuum/increasing atmospheric pressure in the venturi) the Main fuel nozzle continues to flow enough fuel to flood engine unless more air is introduced by opening butterfly a bit. Then it will idle fine all day..... Screw in the H speed screw enough to stop it and it wont rev. I'm hoping I have two defective main fuel ball nozzles. I bumped one pop off to 22psi today just to see if that would stop it. Nope.
Waiting for new ball nozzles now. I'm also making a couple adapters for HL carbs in case this goes on much longer. I'm going through welch plugs like you wouldn't believe. :(

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