Tecumseh 7HP Snowblower carb problem

wolfden793 · Feb 15, 2022

Hi All,

I've been having difficulty with a carb on a Tecumseh 7HP snowblower engine, model HSK70 on a Simplicity blower. I bought a new carb and it ran very nicely until I put the metal cover back and then it ran poorly, mainly revved higher. Difficult to adjust once cover is on except for the main jet on the bowl bottom. Suggestions? Thanks!

4get gto · Feb 15, 2022

The cover shouldn't make a difference. Some covers have a hole inline with the low mixture screw for adjusting. Does it run better without the cover on you say ?
Almost sounds like you have a wrong screw in place somewhere. Only wild guesses. Or your cover is sitting somehow to close to carb opening causing it change with cover installed.

wolfden793 · Feb 15, 2022

4get gto said:
The cover shouldn't make a difference. Some covers have a hole inline with the low mixture screw for adjusting. Does it run better without the cover on you say ?
Almost sounds like you have a wrong screw in place somewhere. Only wild guesses. Or your cover is sitting somehow to close to carb opening causing it change with cover installed.

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wolfden793 · Feb 15, 2022

Hi,

Thanks for your reply. I agree the cover shouldn't make a difference. I've worked on many of these snowblower engines, and none has ever done this. No screws out of place that I know of, just a dome scratcher!

oldnslo · Feb 15, 2022

By runs better is it idling down, flooding out , surging etc?

Richard001 · Feb 15, 2022

Without any photos to see the issue, I would guess that, 1 - the heat cover is blocking the carb intake.
2. The heat cover is interfering with the governor.

Richard

wolfden793 · Feb 15, 2022

Hi Richard,

Thanks for your reply. Hmm, both things worth checking. The guard that is in front of the carb intake spaces the cover from the intake, so don't believe it's coming from there. As to the governor being interfered with, that's a possibility worth checking. Without the cover, I can adjust the carb, although it does surge when the governor screw in turned in. RPM at best setting is about 3100 or so. It's finiky at best, but does run OK without the cover. When I go to put the cover on, I don't even have to put the two carb intake screws on, just get the cover near the intake and it begins to accelerate and won't adjust no matter the position of the throttle control. I welcome your thoughts...

Richard001 · Feb 15, 2022

Can you post some photos of the carb and the governor area ?

wolfden793 · Feb 16, 2022

Hi Richard,

Here are a few pics of my blower. I'll be interested to see what you think.

Richard001 · Feb 16, 2022

Photo #4 shows the float blow vent tube being kinked right at the exit of the carb. You need to change this. Where does the other end of the vent tube go ?
On Photo #7, on the left side of the cover, what does the part that has the sheet metal screw sticking thru it do ?

Can you show photo of the shield installed and look to see if the shield is interfering with the governor arm in that area.

Is this carb an exact replacement part ? For example, did the throttle linkage fit without any bending of the linkage ?

wolfden793 · Feb 16, 2022

Richard001 said:
Photo #4 shows the float blow vent tube being kinked right at the exit of the carb. You need to change this. Where does the other end of the vent tube go ?
On Photo #7, on the left side of the cover, what does the part that has the sheet metal screw sticking thru it do ?

Can you show photo of the shield installed and look to see if the shield is interfering with the governor arm in that area.

Is this carb an exact replacement part ? For example, did the throttle linkage fit without any bending of the linkage ?

OK, the kinked vent tube is the primer tube. The other end fits into the primer bulb. The screw you mentioned doesn't appear to do anything. It's just screwed through the cover and is far from any contact with the engine itself. I put the cover back on and there is no binding anywhere that I can see. Carb is aftermarket and attached without issue or bending of any linkage.

RandyT · Feb 16, 2022

The primer tube is also the bowl vent, so if it kinks can cause richening of the fuel mix due to a siphoning effect. If completely plugged off can even cause it to siphon the contents of the fuel tank.

wolfden793 · Feb 16, 2022

Wow! Didn't know that. Well, I replaced that tube and took it outside just now and it started right up and idled nicely, but if you try and accelerate too quickly, it stalls out. If you try slowly, it's fine. Gotta be a fine adjustment maybe in the governor adjusting screw?

Richard001 · Feb 16, 2022

Nope, has nothing to do with the governor. Your idle adjustment screw needs to be set a little richer as well as the main fuel adjustment screw.

RandyT · Feb 16, 2022

Could be running a tad lean. Try turning the screw out on the side of the carb close to the muffler a small amount and see what happens. If that doesn't correct it then turn the screw out a tad on the bottom of the fuel bowl. From your description it's not getting enough fuel to transition from idle to full speed quickly.

wolfden793 · Feb 17, 2022

Hi Richard,

Thanks for all your help! I adjusted the main jet and idle accordingly and it runs great! I think that kinked tube was the main culprit. Take care and thanks again!

Jim

Richard001 · Feb 17, 2022

Jim,
Glad that it worked out for you. Now when that snow comes around, you will be able to blow it away!

One other thing, that little hole in the primer button must be kept open. This allows the air pressure on top of the fuel in the carb to stay constant.

Richard

wolfden793 · Feb 18, 2022

Hi Richard,

I hope you don't mind another Tecumseh related question. I have an HS50 I'm painting and restoring and as many have found, timing one is a pain. I don't have a dial indicator, but do have a digital caliper. The specs say .080 BTDC, and I measured this distance carefully. I bought a battery powered timing light, but instead of lighting when I reach this point, it just lights to indicate continuity. I've seen several videos online, but they show the light only glows when the "sweet spot" is found. Is my light malfunctioning or am I doing something wrong? Do I need to invest in a dial indicator? New points and condenser, gone through the engine completely. Great compression. Thanks for any help you can offer.

Jim

tomplum · Feb 19, 2022

Well, I'm not Richard. But your life would be easier if you used a ohmmeter /continuity tester rather than a timing light. If you know your gap is .020 at the points and the spec of .080 is correct you should be fine.

wolfden793 · Feb 19, 2022

Hi Randy,
Thanks very much for your message. OK, I'll try and see what I can do with my ohmmeter. I saw a video online where the one used had a tone when the spot was reached and mine doesn't, so I'll just have to experiment and see what happens. Thanks again!

Jim