Major power increase when engine is hot?

DavidCP

Member
Dec 28, 2017
34
8
8
28
I have noticed something curious about my HuaSheng 49cc engine.

It gains significantly more power when the engine gets hot compared to cold. Like roughly 3X more power. The difference is pretty surprising.

Is there a technical reason for this? Is it supposed to be like that?
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
3 times seems like a lot. Is the power adequate before, while warming up?

I've had older, somewhat worn engines smooth out but nothing that drastic a surge in power after warming up.

Thinking some sort of vacuum and as the engine heats, it's sealing itself. But if running well, I wouldn't worry. I would torque everything down to specs. If ya don't have a torque wrench, Make sure everything is at least tight. But be very careful not to over torque and damage anything.

Is it still very cold where you are and how many hours or miles on the engine?

But this will have happened to someone else and they will learn us both. snork.

Did a search but not finding much. If you can and there are no vacuum leaks, post a vid while ridding (sound will be more important) and note at what time you feel (and hear) more power.



(there is 2 "U"s in "vacuum" Man English is crazy. 4 to's, 4 fours...)
2,two,too,to. 4, for, four, fore...Yeah, I know....)
 
  • Like
Reactions: DavidCP

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
Just a thought. Don't let me get ya all wired up and overly proactive. If it ain't broke, don't let some guy on the internet get ya going and help ya fix something until it is broke, LoL.
 

DavidCP

Member
Dec 28, 2017
34
8
8
28
3 times seems like a lot. Is the power adequate before, while warming up?

I've had older, somewhat worn engines smooth out but nothing that drastic a surge in power after warming up.

Thinking some sort of vacuum and as the engine heats, it's sealing itself. But if running well, I wouldn't worry. I would torque everything down to specs. If ya don't have a torque wrench, Make sure everything is at least tight. But be very careful not to over torque and damage anything.

Is it still very cold where you are and how many hours or miles on the engine?

But this will have happened to someone else and they will learn us both. snork.
Well it's still a bit cold where i'm at. It was 28 degrees fahrenheit yesterday. No snow or water on the ground when I tested. High moisture content in the air.

The torque and top speed is pretty bad when the engine is cold. Maybe 10 MPH max speed when cold and jumps to up ~35 MPH max when hot. It feels like an entirely different engine after it gets hot.

I tested it on the same road before and after it got hot (which takes forever in this weather) to compare the difference yesterday.

The engine is still very new. I have put a total of maybe 60 miles on it in total. It gets some pretty incredible gas mileage though. Too early to tell exact numbers but I barely put any gas in it during the time I have taken on it. I suspect this is because i'm reasonably in-shape at 127 pounds.
 

DavidCP

Member
Dec 28, 2017
34
8
8
28
The engine has a metal cover plate. I plan on getting a TrakPower 12V Nitro Engine Heater to put on top of it to help get it up to expected temperature. In this weather the engine takes several miles to heat up. Which on the flipside this means the engine will handle hot summer weather pretty well.
 
  • Like
Reactions: Dan

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
To your point, yes! Amazing little power plants. I personally have only enjoyed owning one other small engine, more.

But these things, not "for the price" but in spite of, are just amazing. Going through the ridiculous reduction so they can drive a bicycle with a 175 lbs man at 35 MPH. And for such a small investment.

Honestly, from an engineering and economic view. Just a great lil' engine. Honda did an amazing job developing these and frankly, HuaSheng did a great job copying.

They get knocked due to the low price and I beg to differ.

And depending on the exhaust and gearing. I just like the way they sound and feel as you ride and experience the engine vibrations.
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
I've never heard of "TrakPower 12V Nitro Engine Heater"

Searching for it now. Really interested and hope others comment on it.
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
https://www.trakpowerusa.com/accessories/index.html

Is this it?

If your gonna enjoy it, ya should get it. I personally think just letting the engine warm up by letting it idle for a minute or 2 would be better for the engine. Not that I think this would do any harm but now the head is warm and the rest is still cold. Rather than the heat migrating naturally. Which, unless in arctic, Siberian extream low temperatures won't harm anything. But the engine would do that just by idling.

Just my opinion and if your gonna enjoy it. Ya should get it. But thinking it's like a boost bottle. Makes sense on paper but doesn't really do any thing for ya.

(LoL, watch. I just started an argument. Ya shoulda been here for the dyno Vs synthetic oil wars of 2002! Many were lost, few were better off and all of us had a beer and laughed at us all)
 

DavidCP

Member
Dec 28, 2017
34
8
8
28
https://www.trakpowerusa.com/accessories/index.html

Is this it?

If your gonna enjoy it, ya should get it. I personally think just letting the engine warm up by letting it idle for a minute or 2 would be better for the engine. Not that I think this would do any harm but now the head is warm and the rest is still cold. Rather than the heat migrating naturally. Which, unless in arctic, Siberian extream low temperatures won't harm anything. But the engine would do that just by idling.
Yes that's it.

The engine takes a long time to heat up. I let it idle for 15 minutes and it was still cold to the touch. So I dunno.
Something weird is going on with it.
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
I have several HS engines and can't remember one that wasn't up to functional in more than a few minutes. Even in the cold.

I've never felt em running, thinking them hot.

Did I miss it, or is that with it warming up with the choke on? (Not sure if that's relevant given your update)

And please forgive any seemingly dumb questions. Honestly and true history. Years back new to MBs guy. Very smart and a nice guy. "My bike won't start" brand new, 2 stroke. For 2 weeks, 3 of us advise him to do everything that can be done. To the point of total tear down and reassembly. I mean every thing. Nothing worked and we all really liked this guy. Again. Very smart and just a good guy.

He posts a picture. His carb was upside down.

So please don't take offense if I ask basic stuff. We all have or will just miss something simple and I never mean to offend.

That's not to say I think you're doing or missing anything. Just hate to annoy with dumb questions.
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
hmm, just a thought. After letting it idle for under a minute. Take her out and see if putting a load on her and see how that works?

Gently at first. I personally go easy on new engines even though producers and suppliers often say there is no break-in period.
 

DavidCP

Member
Dec 28, 2017
34
8
8
28
Ahaha thankfully this came preassembled so unless it was messed up from the factory, it wouldn't be my doing. :)

I do slowly use the choke when riding it. It can go up to 3/4 open? (hard to tell which direction is open) after starting. Any more than that and the engine stalls out.

It was pretty windy yesterday (around 7 MPH wind speed most of the time) so maybe the cold air kept it from warming up?
 

Dan

Staff
May 25, 2008
12,775
109
48
56
Moosylvania
Really hard to see but there is a diagram on the air filter cover with a diagram for choke/open.

As your sitting on the bike. Moving lever to point to your right is choke on. Off or open is to your left.

HS airfilter choke diagram.jpg

Really hard to see. Almost every engine has its own favorites with choke/starting/running. Ya sorta learn each other's ways to happy
 

Greg58

Well-Known Member
May 1, 2011
4,620
1,390
113
63
Newnan,Georgia U.S.A.
I don't own a four stroke but I do know if you are running rich a engine will run cooler, what does the spark plug look like? If it is black its probably on the rich side, check the air filter for debris too. A different plug may help.