Jensim 50cc ATV 4Stroke

techvt · 10-20-2014, 01:22 PM

Anyone know the proper compression for a Hensim 50cc ATV 4Stroke? Ive got one Im trying to get going for my niece but it has no takeoff power. The carb has been thoroughly cleaned, ignition coil replaced, high flow air filter installed and exhaust checked for blockage. So the only other thing I can think of is a comperssion/valve issue. Thanks in advance.

Weldangrind · 10-20-2014, 03:49 PM

Welcome!

It's likely to be similar to any Honda XR50 / CRF50, but I recommend that you head straight for valve adjustment. I'd shoot for 0.002" to 0.003". A little loose is better than too tight.

How did you check the exhaust for blockage?

techvt · 10-20-2014, 03:53 PM

Ok, will check the valve adjustments next.

Just unhooked the exhaust temporarily...I assume thats a valid test.

Weldangrind · 10-20-2014, 04:25 PM

It can be. The stock muffler on most of these little machines are often terrible, with a convoluted and restrictive path for exhaust. If you found little difference when you unhooked it, the muffler isn't too bad in design.

The muffler on my daughter's first 50cc quad was so bad that the engine was a bear to start. Once we opened the muffler up, it warmed up quickly and had a really good power increase.

techvt · 10-20-2014, 07:42 PM

I just checked the valve clearance and the intake was a little tight so I loosened it up a bit and it's still got no power. I weigh about 160 and it'll barely move me on flat ground. I did check the compression with the throttle wide open and I got about 150 psi. What's next?

Weldangrind · 10-21-2014, 12:28 AM

Does it rev while you're trying to ride it, as if a clutch was slipping?

techvt · 10-21-2014, 09:32 AM

No slipping at all...if you lift the wheels off the ground it does rev up fast. Im going to pull the carb apart again for one more cleaning...not sure what else to try. I guess I should ask...should it be able to pull a 160lb adult around on flat surfaces easily?

Weldangrind · 10-21-2014, 12:10 PM

Certainly it should. My daughter's 50cc quad was not only a bear to start and warm up, it couldn't get out of its own way. She would literally get stuck in a shallow tire track.

Once we opened up the muffler, I could tear around the backyard at 200+ lbs.

Have you tried riding it without the muffler?

techvt · 10-21-2014, 04:41 PM

Okay, thanks. I just clean the carb again and no change. Pulled exhaust and tried one more time and no change. I did notice that it low idle it's slowly moves forward. Is the clutch adjustable?

Weldangrind · 10-22-2014, 01:23 AM

It might be. If it is, there will be a flathead screw with a jam nut in the center of the clutch cover.

10-20-2014, 01:22 PM	#1
techvt Join Date: Oct 2014 Posts: 5	Hensim 50cc ATV 4Stroke Anyone know the proper compression for a Hensim 50cc ATV 4Stroke? Ive got one Im trying to get going for my niece but it has no takeoff power. The carb has been thoroughly cleaned, ignition coil replaced, high flow air filter installed and exhaust checked for blockage. So the only other thing I can think of is a comperssion/valve issue. Thanks in advance. Last edited by techvt; 10-20-2014 at 03:39 PM. Reason: spelling
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10-20-2014, 03:49 PM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Welcome! It's likely to be similar to any Honda XR50 / CRF50, but I recommend that you head straight for valve adjustment. I'd shoot for 0.002" to 0.003". A little loose is better than too tight. How did you check the exhaust for blockage? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

10-20-2014, 04:25 PM	#4
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	It can be. The stock muffler on most of these little machines are often terrible, with a convoluted and restrictive path for exhaust. If you found little difference when you unhooked it, the muffler isn't too bad in design. The muffler on my daughter's first 50cc quad was so bad that the engine was a bear to start. Once we opened the muffler up, it warmed up quickly and had a really good power increase. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

10-21-2014, 12:28 AM	#6
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Does it rev while you're trying to ride it, as if a clutch was slipping? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

10-21-2014, 12:10 PM	#8
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Certainly it should. My daughter's 50cc quad was not only a bear to start and warm up, it couldn't get out of its own way. She would literally get stuck in a shallow tire track. Once we opened up the muffler, I could tear around the backyard at 200+ lbs. Have you tried riding it without the muffler? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

10-20-2014, 03:53 PM	#3
techvt Join Date: Oct 2014 Posts: 5	Ok, will check the valve adjustments next. Just unhooked the exhaust temporarily...I assume thats a valid test.
	0

10-20-2014, 07:42 PM	#5
techvt Join Date: Oct 2014 Posts: 5	I just checked the valve clearance and the intake was a little tight so I loosened it up a bit and it's still got no power. I weigh about 160 and it'll barely move me on flat ground. I did check the compression with the throttle wide open and I got about 150 psi. What's next?
	0

10-21-2014, 09:32 AM	#7
techvt Join Date: Oct 2014 Posts: 5	No slipping at all...if you lift the wheels off the ground it does rev up fast. Im going to pull the carb apart again for one more cleaning...not sure what else to try. I guess I should ask...should it be able to pull a 160lb adult around on flat surfaces easily?
	0

10-21-2014, 04:41 PM	#9
techvt Join Date: Oct 2014 Posts: 5	Okay, thanks. I just clean the carb again and no change. Pulled exhaust and tried one more time and no change. I did notice that it low idle it's slowly moves forward. Is the clutch adjustable?
	0

10-22-2014, 01:23 AM	#10
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	It might be. If it is, there will be a flathead screw with a jam nut in the center of the clutch cover. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0