RPM issue with cheap brand Hangkai

mangoboxer

Cadet
Joined
Sep 5, 2017
Messages
8
Good day, I was on a limited budget, and decided to buy a cheap 6 hp Hangkai motor from China for my 14 foot inflatable kaboat. Immediately I noticed, that I wasn't getting the speed I was expecting (about 10 to 12 mph.) I was doing about 5 mph instead. I have been troubleshooting this problem for months, and I know it is capable of more power, because a couple outings I had a nice burst of speed for a while until I turned off the motor for a bit, went on a plane. Now, I have no idea why this speed happened. Here is what I have tried; took apart the carb multiple times and sprayed with carb cleaner, checked float, checked needle valves, checked fuel lines, replaced spark plug, played around with the mixture screw to no success, and checked fuel pump. I measured the rpms, and maxes out at 3400 when it should do 5500, which is can idle at. When the motor is in a test can, the motor seems to go in and out of of a lot of rpms, even seems like it becomes more powerful when the cover is off. But it seems to go back to the same old 3400 or lower when the motor is under load on my boat. I am at a loss here, and no mechanic wants to look at my motor because it is an off-brand. Any help would be appreciated, thank you.
 

flyingscott

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Apr 8, 2014
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Is your motor a 2 cylinder, if it is look for spark on both cylinders.
 

robert graham

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Apr 16, 2009
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If it in fact runs better with the upper cowling off then you may have an exhaust leak or a restriction in the air intake of the cowling....just a thought..
 

mangoboxer

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Sep 5, 2017
Messages
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If it in fact runs better with the upper cowling off then you may have an exhaust leak or a restriction in the air intake of the cowling....just a thought..
If it is water cooled is there still an air intake? Where would an exhaust leak take place? Thanks
 

tomhath

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Dec 5, 2007
Messages
814
One cylinder, two-stroke motor. I wouldn't expect the problem to be spark related.

Maybe the throttle linkage binding somewhere?
 

mangoboxer

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Sep 5, 2017
Messages
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One cylinder, two-stroke motor. I wouldn't expect the problem to be spark related.

Maybe the throttle linkage binding somewhere?
I just checked with the spark tester, it is consistent with an orange spark. Not sure about a binding, is the throttle linkage the wire that is connected to the throttle which moves up and down as I give it throttle?
 

robert graham

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Apr 16, 2009
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If it is water cooled is there still an air intake? Where would an exhaust leak take place? Thanks
Try running the motor with the cowling off....if it's an exhaust leak or restricted air inlet then it'll run better with the cowling off....
 

mangoboxer

Cadet
Joined
Sep 5, 2017
Messages
8
Try running the motor with the cowling off....if it's an exhaust leak or restricted air inlet then it'll run better with the cowling off....

When I run it in a test tank and the cowling off, it seems to sometimes get a boost of rpms then goes down again. It does it in spurts. I don't know how it would have a clogged exhaust when it is practically a new motor. When you say air inlet, are you talking about on the side of the carb? Because there is no inlet on the cowling.
 

3rdtimesthecharm

Petty Officer 1st Class
Joined
Jul 29, 2010
Messages
283
Have a fan blowing across it while in the test tank to get the exhaust away so it doesn`t breathe it`s own fumes.
 

funk6294

Petty Officer 1st Class
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Apr 26, 2009
Messages
294
Does the motor sound like its blubbering when it won't hit rpm, or is it bogging?
 

funk6294

Petty Officer 1st Class
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Apr 26, 2009
Messages
294
If it's bogging then it's running lean. You might try adjusting the mixture screw an 1/8~1/4 of a turn out to riches up the carb.
 
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