HS50 Slowly Revving At Idle

#1
Hey there OldMiniBikes,

I have an HS50 (67089A, electronic ignition) that seems to be slowly speeding up at idle. It has an eBay carb on it, specifically the one in this kit.

On 1/3 choke, the engine plugs along fine, but upon releasing the choke, the engine begins to speed up. Ill be honest; I haven't a clue whats causing it and am considering getting a different carburetor.
 
#2
Hey there OldMiniBikes,

I have an HS50 (67089A, electronic ignition) that seems to be slowly speeding up at idle. It has an eBay carb on it, specifically the one in this kit.

On 1/3 choke, the engine plugs along fine, but upon releasing the choke, the engine begins to speed up. Ill be honest; I haven't a clue whats causing it and am considering getting a different carburetor.
I would do three things in some order:
Go to the manual that is a sticky on this forum and review the troubleshooting section on your symptoms. It is pretty easy to use and follow.

Verify the governor is set properly, functioning properly. The governor spring and linkage must be working correctly for accurate speed control.
Replace the spring and linkage if suspect.

Prior to installing an aftermarket carb, remove the bowl and inspect the internals. Verify the valve and seat, float mechanism and float setting. Check any mixture screws for recommended initial settings. Clean the fuel tank, replace the lines and filter.

The spark plug will look like it’s running rich.
Hope this helps.
 
#4
I would do three things in some order:
Go to the manual that is a sticky on this forum and review the troubleshooting section on your symptoms. It is pretty easy to use and follow.

Verify the governor is set properly, functioning properly. The governor spring and linkage must be working correctly for accurate speed control.
Replace the spring and linkage if suspect.

Prior to installing an aftermarket carb, remove the bowl and inspect the internals. Verify the valve and seat, float mechanism and float setting. Check any mixture screws for recommended initial settings. Clean the fuel tank, replace the lines and filter.

The spark plug will look like it’s running rich.
Hope this helps.
Oh, check the throttle installation in the carb, they should easily operate with no undue sloppiness or resistance to movement.
 

Ding Ding

Well-Known Member
#5
The spring going from the governor arm to the throttle linkage is likely trying to "spring" back to being shorter, thus pulling on the governor arm and increasing the idle. Try stretching the spring a little bit to relieve the spring tension.
 

I74

Well-Known Member
#8
Sounds like a possible ''false air'' condition to me.
If it idles steady with a little choke, but revs. up with out it, my first thought is that the carb or intake,, might have an air leak.
I would check the throttle shaft for play, & spray ''just a smidge'' of carb cleaner ect. ''with it running'',, where the shaft comes out of the carb body, & also spray a smidge around the intake mating surfaces,, & see if you notice a different rpm change.;)
I
 

joshua. c.

Well-Known Member
#10
sounds to me like an adjustment issue. running faster means running better, so its not a tuning issue. make sure the throttle plate returns to the stop screw at idle. if it dose return and its still revving then back the screw off until it slows down. if it dosn't return to the stop screw your linkage is screwed up or not properly adjusted some how.
 
#11
Alright I'm gonna hijack my own thread (sorry me!) and ask a different question: Two of the side cover bolts broke off inside the block, how screwed am I?
 
#12
Can you weld? I have removed broken bolts by welding on the bolt and building it up until you can get a pair of vice grips on it.
Otherwise you are looking at drilling them out.
 
#13
Can you weld? I have removed broken bolts by welding on the bolt and building it up until you can get a pair of vice grips on it.
Otherwise you are looking at drilling them out.
One of the bolts is far enough out to get a small vice grip on to, the other is sunken into the block. Pics to come.
 
#15
In the past, i have done it by sticking the tungsten way out, and just letting the heat soak a little then start adding filler.
Then let off the pedal for a sec, then ramp up and add more filler, repeating until it is proud of the hole.
The fact that it is a steel bolt in an aluminum block is helpful, as the aluminum will not readily weld to the steel, especially on DC.

When I watched that video, all I could think of is The Young Ones lmao
 

joshua. c.

Well-Known Member
#16
have you tried soaking it in penetrating oil for a week and using an easy out to remove it? make sure its fully centered on the bolt or it won't turn. it woold help to grind the top flat first and center punch it.. taping on the bolt a few times lightly with a hammer after oiling it and before the easy out should help loosen it a bit. and if that method or any of the others listed dont work you can always drill it out and re thread the hole for a helicoil ( a double sided thread made to be screwed into a larger threaded hole to downsize it to a smaller thread diameter.).
 
#17
The old timers used to heat it and use a candle to wick the wax between the threads lol
Seen it work with my own eyeballs.
Gotta use low heat tho

But seriously, side cover bolts should be fairly easy to heat and remove, as there is good access to that part of the engine to heat it
 
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