Honda CH150 - rough idle - smooth at acceleration

RoaringTodd · Post by **RoaringTodd** » Mon Sep 16, 2013 1:23 pm

Good Morning Buddyland -

CH150 Carb manifold replacement was a success. Had no problems.

However, continue to have the issue of rough idle. When the scoot is idling, the engine is really shaking. However once throttle is applied, its smooth sailing. I love that engine's oomph.

I am 80 percent convinced it is a carb issue because once fuel flow is increased, its smooth. Has anyone had any experience with this?

RT

edited to correct spelling errors.

Throwback7R · Post by **Throwback7R** » Mon Sep 16, 2013 4:33 pm

turn up the idle speed.

RoaringTodd · Post by **RoaringTodd** » Mon Sep 16, 2013 4:40 pm

Throwback7R wrote:turn up the idle speed.

Yeah, tried that. Still rough...

lovemysan · Post by **lovemysan** » Mon Sep 16, 2013 4:54 pm

Mixture screw? Plugged pilot jet? Plugged throttle butterfly air bleed? Stuck auto enrichment solenoid? All guesses I'm not familiar with your carb. Bad fuel will cause this as well.

Stitch · Post by **Stitch** » Mon Sep 16, 2013 5:11 pm

I'd clean the jets. Ethanol is nasty stuff.

tortoise · Post by **tortoise** » Mon Sep 16, 2013 5:12 pm

CH150 service manual pdf
3-6 valve clearance
3-9 cylinder compression
4.0 fuel system

charlie55 · Post by **charlie55** » Mon Sep 16, 2013 5:38 pm

Let it idle for 10 minutes and then pull the spark plug. (BTW - did you install a new plug or clean/re-gap the old one?). If it's carbon-fouled, then your idle mix is too rich. If that's the case then, as others have opined, either your idle mixture screw needs to be adjusted or your auto bystarter (electric choke) is failing to shut. Given the vintage of the scooter, I'm more inclined to think it's the latter. Bystarters are electrical components and are prone to age-related failures.

If you didn't replace or clean the plug, then do so before performing this test so as to insure that any carbon buildup is new and not just accumulated over the years.

Robbie · Post by **Robbie** » Mon Sep 16, 2013 9:17 pm

I dunno.....I remember the engine wiggled like a wet dog at idle, but the mounts were so good you could barely feel it in the chassis.

Don't remember any particular problems causing rough idle beyond what you found.

Rob

RoaringTodd · Post by **RoaringTodd** » Tue Sep 17, 2013 11:28 am

Thanks everyone for their help and tips. I am planning a trip from Philly to RVA for the 7 Hills Rally, and am working on getting Big Abigail ready for the long trip.

Cheers -

RT

tortoise · Post by **tortoise** » Tue Sep 17, 2013 1:58 pm

RoaringTodd wrote:I am planning a trip from Philly to RVA for the 7 Hills Rally, and am working on getting Big Abigail ready for the long trip.

Might be prudent to include the front wheel bearings in your preventative maintenance . . cross-country reference.