Tecumseh HS40 cuts out when I try to accelerate

[Rupp_It_Up]

I have 72 Rupp with a 4hp tecumseh motor that will idle fine but stalls out when I give it the gas. It has new head gasket, points, condenser, coil & spark plug. I'm using a carb off another bike that runs perfect on the other bike. I set the points at .020 and the timing at .035. BTW- When I got the motor it wouldn't start because the timing was off at .060.
It looks like a low mileage motor because I could see the crosshatch lines on the cylinder.
Thanks in advance for you help.

 

[massacre]

I had this issue on an Hs50 a while back and it turns out the float level was too low.
Not saying it will fix your issue but it did fix mine.

This given that your jets are set up correctly

 

[Rupp_It_Up]

I had this issue on an Hs50 a while back and it turns out the float level was too low.
Not saying it will fix your issue but it did fix mine.

Thanks for the response. I agree that it does seem like it's not getting enough gas.
During the process of elimination I installed a carb that was working perfectly from a similar motor and it still sputters and then cut out during acceleration.

 

[Rupp_It_Up]

I have also tried different timing settings...
.020" points gap .030 timing
.018" points gap .030 timing

 

[massacre]

I would keep the factory points gap, plug gap, spark advance, etc.
If you can get it to start and idle, then let the carb warm up and then set it according the the tec manual available on here for free anytime day or night

http://www.smallenginesuppliers.com...cumseh_L-Head_Engines_Service_Information.pdf

 

[cfh]

your rupp is 20 degree mount. does the intake accommodate this?

 

[Rupp_It_Up]

your rupp is 20 degree mount. does the intake accommodate this?

Yes, I have a 20 degree slant intake. The motor is completely stock.

 

[Rupp_It_Up]

I would keep the factory points gap, plug gap, spark advance, etc.
If you can get it to start and idle, then let the carb warm up and then set it according the the tec manual available on here for free anytime day or night

http://www.smallenginesuppliers.com...cumseh_L-Head_Engines_Service_Information.pdf

I started with the factory settings for carb, points & timing. BTW- I've been restoring Rupp's for 25 years and never had this much trouble getting an engine to run properly.

 

[massacre]

The closest I ever came to having a perfectly operating stock tec carb was by following these procedures.
I put my bike up against a concrete wall up on a milk crate to set the high speed jet. Once that was set the idle stuff was easy and the bike ran great

 

[massacre]

Sorry just read your post.
Was just throwing stuff out there.

Some type of vacuum leak? Compression leak?
If the engine is set up correctly than I am just as confused as you are

 

[SAT]

I have 72 Rupp with a 4hp tecumseh motor that will idle fine but stalls out when I give it the gas. It has new head gasket, points, condenser, coil & spark plug. I'm using a carb off another bike that runs perfect on the other bike. I set the points at .020 and the timing at .035. BTW- When I got the motor it wouldn't start because the timing was off at .060.
It looks like a low mileage motor because I could see the crosshatch lines on the cylinder.
Thanks in advance for you help.

I would start with the easy stuff. Check for any intake gasket leaks, especially at the 6 o’clock position. Use an inline spark tester on it.
Check for head gasket leaks. Check and clean the carb fully. It probably needs it anyhow.
I would start with these.
Are there fresh tool marks on the head and casing bolt heads?
Hope this helps

 

[Rupp_It_Up]

I would start with the easy stuff. Check for any intake gasket leaks, especially at the 6 o’clock position. Use an inline spark tester on it.
Check for head gasket leaks. Check and clean the carb fully. It probably needs it anyhow.
I would start with these.
Are there fresh tool marks on the head and casing bolt heads?
Hope this helps

I put installed a new head gasket. It also has a new slant intake with new carb/intake gaskets.

It seems like either an intake leak or carb issue but I'm using a carb from another bike that runs great.

What did you mean by fresh tool marks on the head and casing bolt heads?

Also, what did mean by using an inline spark tester on it to check for intake leaks?

 

[jeep2003]

Do you have good fuel flow to the carb? First try to richen the high speed and if that doesnt do it I would clean out the bowl and bowl screw even though you switched carbs.

 

[Rupp_It_Up]

I'm using fresh gas and cleaned out the bowel and high speed screw.

Initially, I rebuilt the original carb and to confirm it worked properly, I tested it on a bike that runs. When I put the rebuilt carb on the problem motor, the engine didn't would only idle. That's when I decided to switch carbs.

I'm getting the same results on the poorly running motor with two carbs that run fine on another motor.

Then I started trying different points gap/timing set ups. But nothing has worked so far.

 

[John G.]

Do a compression check, if compression is ok then check your valve clearances.

 

[jeep2003]

People say the coil can do that too but I havnt seen it personally.

 

[Rupp_It_Up]

People say the coil can do that too but I havnt seen it personally.

I also put in a new coil and it didn't help, but thanks for all of your suggestions.

 

[Skipp]

I had a similar occurrence today idled fine under load or after a rev it would just die...a pull or two and it hesitantly fires....changed out the gas and it ran just fine...read somewhere recently not to keep ANY gasoline more than 30 days no matter the additive you put in it...ie stabil etc...just a simple thought...

 

[SAT]

I put installed a new head gasket. It also has a new slant intake with new carb/intake gaskets.

It seems like either an intake leak or carb issue but I'm using a carb from another bike that runs great.

What did you mean by fresh tool marks on the head and casing bolt heads?

Also, what did mean by using an inline spark tester on it to check for intake leaks?

My bad.
Wrenches leave telltale marks on bolt heads and the surrounding area, an indication that someone has had it apart before you got it.
My in-line tester is used any time I think the ignition is at fault. I like the Oregon with the little orange light. I should have separated it from the intake leak issue. It sounds like it’s leaning out when you advance the throttle. I would still check for an intake gasket leak.

 

[SAT]

My bad.
Wrenches leave telltale marks on bolt heads and the surrounding area, an indication that someone has had it apart before you got it.
My in-line tester is used any time I think the ignition is at fault. I like the Oregon with the little orange light. I should have separated it from the intake leak issue. It sounds like it’s leaning out when you advance the throttle. I would still check for an intake gasket leak.

With a sick engine, I go back to the L Head Service Manual dozens of times to help keep me on track.