hensim 150cc motor bogs when full throttle

Danthalis · 05-25-2009, 01:13 PM

Wanted to see if I could get some opinions on this problem.

My friend has a 150cc hensim engine and recently had the engine rebuilt. Now we can get it to start, but anything over 1/2 throttle the bike starts backfiring and bogging down until it stalls.

My friend who rebuilt it is pretty good with engines, and thinks it's the timing chain is stretched. he tried moving the chain one tooth and the engine would not start at all so now we're kinda at a loss.

Anyone else seen something like this before? Thanks

KentuckyDonkey · 05-25-2009, 04:49 PM

Sounds like the carb, to me.

I'd take 'er off and clean it out and then set the mixture screw at two turns out (after having turned it all the way in), and check the float. Put 'er back on, and see how she does. Maybe play with the mixture if need be after that- then see what happens. (If the old engine was really worn, the carb may have been adjusted over time to compensate for the engines wear and poor performance...and if it wasn't rebuilt/readjusted when the new engine was installed, it may be the problem)

May seem obvious, but don't forget to check the air filter and fuel filter/flow from the tank, too.

Check for leaks/loose bolts around the intake manifol/carb mount too....

Suspect the simple things first...because that's where the problem will most likely lie.

TheRealWorld · 05-29-2009, 12:24 AM

If it runs OK at medium speed, and bogs out like described The Kentucky Donkey hit it right on the head

May seem obvious, but don't forget to check the air filter and fuel filter/flow from the tank, too.

And then float and main jet.

KentuckyDonkey · 05-29-2009, 01:37 AM

The beauty of it is, with these bikes, they are so simple, even if a person doesn't know what they are doing(like me!)...they can figure it out. The way these carbs work becomes apparent as soon as you open one up. Simplicity itself!

If only cars and everything else these days were still this simple!

I think my first item to check if I were OP, would be the intake to engine and carb to intake bolts/nuts. They were loose on two of the three china bikes I've had thus far, out of the crate.

Funny thing, with my Vbike 250T, on which I was having the same problem as the OP, it was a combo of several of those things: There was an insect part in the carb; the intake to engine bolts were loose and the float was cutting off the gas too soon, to allow enough gas to be in the bowl for when the throttle is floored.

My 300M didn't bog- but didn't idle the greatest...so I gave it the carb remove/clean/replace and bolt-tightening routine...and it improved it's idle and even tweaked it's performance 100%.

From now on, any new China bike I get..the carb comes off and gets cleaned/adjusted from the git-go!

Danthalis · 05-29-2009, 10:24 AM

WE had a bit of bad weather here so I've not had the opportunity to get to my friends ATV but I certainly will give this all a try. I built a carb back in high school so heh hopefully I'll be okay. I really appreciate the help and when I finally do get to it I'll be sure to let yall know how it goes.

05-25-2009, 01:13 PM	#1
Danthalis Join Date: Mar 2009 Location: Silver Springs, NV Posts: 45	hensim 150cc motor bogs when full throttle Wanted to see if I could get some opinions on this problem. My friend has a 150cc hensim engine and recently had the engine rebuilt. Now we can get it to start, but anything over 1/2 throttle the bike starts backfiring and bogging down until it stalls. My friend who rebuilt it is pretty good with engines, and thinks it's the timing chain is stretched. he tried moving the chain one tooth and the engine would not start at all so now we're kinda at a loss. Anyone else seen something like this before? Thanks __________________ Vbike V4-SW 250cc
	0

05-29-2009, 10:24 AM	#5
Danthalis Join Date: Mar 2009 Location: Silver Springs, NV Posts: 45	WE had a bit of bad weather here so I've not had the opportunity to get to my friends ATV but I certainly will give this all a try. I built a carb back in high school so heh hopefully I'll be okay. I really appreciate the help and when I finally do get to it I'll be sure to let yall know how it goes. __________________ Vbike V4-SW 250cc
	0

05-25-2009, 04:49 PM	#2
KentuckyDonkey Join Date: Feb 2009 Posts: 331	Sounds like the carb, to me. I'd take 'er off and clean it out and then set the mixture screw at two turns out (after having turned it all the way in), and check the float. Put 'er back on, and see how she does. Maybe play with the mixture if need be after that- then see what happens. (If the old engine was really worn, the carb may have been adjusted over time to compensate for the engines wear and poor performance...and if it wasn't rebuilt/readjusted when the new engine was installed, it may be the problem) May seem obvious, but don't forget to check the air filter and fuel filter/flow from the tank, too. Check for leaks/loose bolts around the intake manifol/carb mount too.... Suspect the simple things first...because that's where the problem will most likely lie.
	0

05-29-2009, 12:24 AM	#3
TheRealWorld Join Date: Jun 2008 Posts: 817	If it runs OK at medium speed, and bogs out like described The Kentucky Donkey hit it right on the head May seem obvious, but don't forget to check the air filter and fuel filter/flow from the tank, too. And then float and main jet.
	0

05-29-2009, 01:37 AM	#4
KentuckyDonkey Join Date: Feb 2009 Posts: 331	The beauty of it is, with these bikes, they are so simple, even if a person doesn't know what they are doing(like me!)...they can figure it out. The way these carbs work becomes apparent as soon as you open one up. Simplicity itself! If only cars and everything else these days were still this simple! I think my first item to check if I were OP, would be the intake to engine and carb to intake bolts/nuts. They were loose on two of the three china bikes I've had thus far, out of the crate. Funny thing, with my Vbike 250T, on which I was having the same problem as the OP, it was a combo of several of those things: There was an insect part in the carb; the intake to engine bolts were loose and the float was cutting off the gas too soon, to allow enough gas to be in the bowl for when the throttle is floored. My 300M didn't bog- but didn't idle the greatest...so I gave it the carb remove/clean/replace and bolt-tightening routine...and it improved it's idle and even tweaked it's performance 100%. From now on, any new China bike I get..the carb comes off and gets cleaned/adjusted from the git-go!
	0