Wake up your Huasheng 142F

[Scootmeister]

I have been riding my HS-powered bike for several years now. Originally, I rode with a direct chain drive, but performance was marginal. I finally broke down and bought a SBP shift kit and added a Shimano 3 speed hub and my takeoff and top end improved, but the engine was still anemic, even though it is dependable, quiet, and easy to maintain. Last week I bought a SBP free flow air cleaner and even though it is pretty narrow, it was a tight fit. The engine obviously was running too lean so I started researching how to re-jet. I finally found a go kart website with excellent instructions for drilling out the stock jet on the stock carb. I know you have heard a lot of advice about how to get more out of these little engines. Do yourself a favor. Get a set of wire drill bits with a range of #60 to #80. Remove your carb and pull the jet. Carefully drill out to .260 (#70 or 71) and install a free flow air filter. Attached is a picture of the moped air filter I used. I fabricated a mount from a 3/4" chrome flange for a handrail for a boat. It is 45 degrees so it allows the cone filter to clear the center post. I centered the center hole for the flange over the stock filter and marked the mounting holes. I drilled the mounting holes to match the pattern of the carb. The same bolts hold the carb and the flange to the intake port. The chrome flange was $4 from a marine salvage shop and the cone filter was $11 online. The engine gained noticeable horsepower and the filter can now be changed by simply removing the hose clamp. With the SBP filter, I had to remove my engine to change the filter. The difference this modification made is amazing. It's still not a screamer, but at least it's not a crawler anymore. I don't need to over rev the engine because of my gears, so I don't expect serviceability to suffer.

 

[Scootmeister]

I improved this installation with the addition of a brass fitting for the small rubber tube that vents air from the crankcase to the carb. I used a die with pipe threads.

 

[wheelbender6]

Nicely done. Sounds like jetting can make a dramatic difference in some four strokes. Much cheaper than a bigger cam and valves.

 

[Davezilla]

Yup... Nicely done, and Yes, jetting has the same effect on 4 strokes too... correcting the air fuel ratio in any engine will give the best performance and fuel efficiency.

 

[scotto-]

I just opted for a larger carb and drilled the jet to go with free flow intake, the cam, stiffer valve springs and a custom exhaust. Did some port work as well

 

[The_Aleman]

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[Scootmeister]

Hi Scotto and Aleman. How much difference did your custom exhaust make? I'm still using my old poo poo pipe which is extremely quiet but also restrictive. I'm thinking about going to a Supertrapp for Honda 50s. Would need to fab a pipe. I just took the bike out and I can't imagine going back to a stock HS. With the 3 speed hub it rides like a little motorcycle now that its got more oomph. I read somewhere that tuning the carb on these engines adds another horse. Maybe could get a little more with a tuned exhaust.

 

[KCvale]

I finally broke down and bought a SBP shift kit and added a Shimano 3 speed hub and my takeoff and top end improved

Yes indeed, I really like a JS and 3-speed, that's all the gear range most need and you can run single speed chain to the back wheel.

Nice work with improvements.

 

[The_Aleman]

<removed out of protest to certain "staff" practices in this forum.>

 

[Scootmeister]

I hear you KC. The best thing about this modification is that the increase in power is most noticeable at lower RPMs so I don't have to over rev the engine to ge it going. The increase over the stock output is very noticeable and makes this little engine viable where it was just marginal. I can't wait to come up with an open pipe and see how that effects performance.

 

[The_Aleman]

<removed out of protest to certain "staff" practices in this forum.>

 

[Scootmeister]

That's fine. My wheelie days are over. I'd rather have a little more on the high end at this point. I'm fabricating an open pipe so I can compare the two and pick the one that I like the best (My daily rider is a Harley Road King, so noise is not a problem for me, at least when it's coming from a bike).

 

[The_Aleman]

<removed out of protest to certain "staff" practices in this forum.>

 

[Scootmeister]

I ordered a Scrambler type pipe from Phantom Bikes earlier this week. It's basically a header with the end wrapped in glass then covered with a larger exhaust pipe. I bought the cap for a more finished look. When it comes in I'll slap her on and take some photos. It's totally unrestricted so I'm expecting to like it a lot. I like the fact that the pipe fits on the right hand side and it's high. I could have made one from the header to my stock pipe, but I didn't wan to cut the nut off in case I want to swap out between the scrambler pipe and the poo poo pipe.

 

[dirtwarrior]

interesting mods indeed

 

[KCvale]

Well, my SBP 4G and Sturmey X-RD5 give me a 35.15:1 reduction in 1st gear. At HS torque peak of 4500RPM, I'm going 10MPH and my chevroleg cadence is 65RPM.
Total torque generated at that speed is well over 100 ft/lbs and so the front end will come up easily. My bike does 0-30MPH in about 4 seconds.

Don't ya just love that feeling?
Gears change everything and I'm an internal shifter hub fan.

 

[dirtwarrior]

I am going to do a FD with this same engine. With the low restriction air filter and the cigar type muffler what exactly was the jetting change wit both mods?
What hp difference do you think happened?
Do I need a drill press to drill the jets? Can I do it spinning the bits by hand?

To do the intake and exhaust mods what needs to be done?

 

[Scootmeister]

Hi Dirtwarrior. The jet is soft brass and the amount removed is so minimal that you might be able to do it by hand. I used a dremel and the bit went through like a hot knife through butter. The difference in horsepower is noticeable, the engine now revs like a motorcycle engine instead of a rototiller engine, if that makes any sense. The sound of the exhaust is also considerably different. It's now crisp and sharp instead of dull and muffled. It's like a totally different engine.

 

[dirtwarrior]

The sound of the engine makes total sense to me, it breaths much freer
OK with the intake and exhaust mods what drill bit size did you use?

The intake and exhaust mods can you tell me step by step how you did them?

 

[Scootmeister]

I have been told you can go as high as .292. I followed the guidelines of people who build racing engines and went with .260.