Tohatsu 8hp 2 stroke carburator issue

[boatwiser]

Hope someone can help me on this - I must be missing something.

My old faithful 8hp Tohatsu that has never given me a problem in over 20 years started running poorly for my son last time out and finally wouldn't keep running. I pulled the carb off and took it all the way down and cleaned all jets and passageways with carb clean and compressed air. Drained and flushed the gas tank and hose and filled with fresh gas. Changed out the engine gas filter. Checked compression - both cylinders around 115lbs. Checked spark and changed out the plugs.

Fired it back up and engine idles very low and dies out. If I keep it running by using the choke I can get my inflatable up on plane but cannot get full power out of it. Pulled the plugs and found one to be blackish and the other to be like it was never used.

Took the carb apart a second and third time with same results.

Could I have reversed the low and high speed jets or is that not possible? I checked out a diagram of the carb online and I believe it shows the rubber cap over the low speed jet. I think I have the rubber cap over the high speed jet - the jet that has the nozzle attached.

Any ideas??

 

[pvanv]

Re: Tohatsu 8hp 2 stroke carburator issue

If you had a carb problem, you are only halfway home. Spray carb cleaner is not strong enough to dissolve varnished organics in the slow-speed passages. You need to do a complete disassembly, and a dunk in real carb dip, such as Tyme. You can use carb spray to wash off the carb dip when the soaking is done, but warm water works equally well.

As for the jet assembly, you may have a problem. Yes, the high-speed or main jet is the master feed for everything. It holds the emulsion tube "nozzle" in the body. The fuel for the low-speed jet must pass through the main jet area first, and if the rubber plug is not covering the port below the slow speed jet, the motor will run way rich at speeds below WOT. On the other hand, if you have the slow jet wide open, and have plugged the main, you will have really strange mixtures across the entire RPM range.

 

[boatwiser]

Re: Tohatsu 8hp 2 stroke carburator issue

Do you know if it is physically possible to screw the low speed jet into the main jet threads and the main jet into the low speed threads? The diagram I looked at did show the plug below the slow speed jet. The slow speed jet looks as it has a bigger hole in it than the main jet that has the tube/nozzle attached - is that correct?

Thanks

 

[boatwiser]

Re: Tohatsu 8hp 2 stroke carburator issue

Okay - I took the carb apart again and confirmed jet positions. The way I have them in is the only way they can be. The smaller jet that has the tube nozzle also has the rubber cap covering it - the larger jet is not covered.

Took all apart again and cleaned again with spray carb clean and compressed air, even though it looks clean as new - motor will only start after a couple of pulls with the choke all the way on - runs rough and stalls at idle - I unscrewed the mixture screw from about 1 3/4 turns out to over 3 turns and that helps the idle but still will stall out with throttle all the way backed off.

I can get the motor to rev up after it bogs and stumbles through the mid-range. Dirt still somewhere? Weak fuel pump or does that work or not work?

 

[pvanv]

Re: Tohatsu 8hp 2 stroke carburator issue

To reiterate... It sounds like you have varnishing in the low speed circuit... If you have a carb problem, you are only halfway home.

Spray carb cleaner is not strong enough to dissolve varnished organics in the slow-speed passages.

You need to do a complete carb disassembly, and a dunk in real carb dip, such as Tyme. You can use carb spray to wash off the carb dip when the soaking is done.

 

[boatwiser]

Re: Tohatsu 8hp 2 stroke carburator issue

Thanks - that will be the next step. I'll post back after a weekend dip in some HD carb cleaner.