Help! 4 strokin' and Bogging Down as I Speed Up!

racereeves

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Jun 6, 2008
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It happened again today. I forgot I had my petcock turned off and it started right up as usual. Ran sluggishly as I got faster...as usual, then it finally kicked into that usual 2 stroke cycle like it should right before it ran out of gas. Respectfully put, I really don't think I'm not getting enough gas but too much. It tops out at 19/20 mph. I am completely frustrated. I thought about it all night and decided to bend the float tangs down so as to shut off fuel to the bowl sooner. That proved to make little to no difference. If someone can give me a good explaination of what's going on I would greatly appreciate it. I'm one who need to know the "why" behind the "how". I'm sure many of you can understand that. Terribly ready to make it a cummuter but can't until I'm sure it's running properly.

Thanks for reading!
 

brydonb

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Jun 6, 2008
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do you know the rpm that your engine is running? Have you tried running with your choke in different positions?
 
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racereeves

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Jun 6, 2008
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I have tried the choke and the problem gets worse. I'm not sure what the rpm is. I know that it's four stroking because it's running rough. every now and then as I back off of the throttle it goes into 2 stroke mode. I don't run it hard. I don't think the rpm is too high. I've been thinking about air leaks. I think the little primer button is leaking air into the bowl. What do you think? I'm goint to either remove it and seal it somehow or try and find an o-ring that's small enough to go around the base of it. Again, what do you think? Thanks for reading!
 
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Jun 3, 2008
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doesn't matter if the primer is leaking air, the bowl needs to vent and has a vent, or a vacuum would occur in the bowl and it would lean out and stop, check your plug for color, they run fast and clean when they are lean, its a fine line tuning a 2 stroke, to lean will burn the piston and over rich will make it miss fire, hense why it runs good before it runs the bowl dry when the fuel tap is off.
If your plug is damp it is rich, over rich is probaly most of your problem.
 

racereeves

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Jun 6, 2008
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The plug is damp. I thought it was running rich. I've moved the clip on the needle to the very top but I'm still running rich. How do I get it to run leaner? I also thought about trying to turn the petcock on just a little bit and not all the way and see if that might help. Tried it a little yesterday though and it didn't help. I put an o-ring between the carb and intake manifold so I don't think there's an air lean anywhere.
 
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Nah not an air leak, you would have a clean plug, changing the needle setting wont effect WOT (wide open throttle) main jet controls WOT and the needle controls part throttle and cruise mixture.
The standard carb on a HT motor can be difficult to tune because of the design, it has no idle circuit and no cut out in the rear of the slide so you find the idle screw has minor or no affect on idle speed so you tend to wind the cable up a bit to get it to idle, which in affect pulls the needle up through the emulsion tube and gives the engine a rich mixture on part throttle.
The ignition is weak also and can cause it to run in a rich condition (doesn't complete combustion), if you have'nt allready, try changing the plug to a NGK or champion and set the gap at 0.025" _ 0.030"
 

racereeves

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Jun 6, 2008
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Do you know what the item number on the spark plug is? I could stop at Wally world on my way home to pick one up. There's also a motorcycle shop on my way (where I get my Amsoil). The plug is gapped at about .035 now. I think you hit the nail on the head! I'd like to change out the wire but the cdi is sealed. Can't crack it open. The throttle cable adjustment screw on the top of the carb is all the way down in my attempt to get the needle as low into the carb as possible. I did, however, catch an error of mine. I put the clip of the needle UNDER the slotted silver retainer disk which, if the needle has bottomed out would cause the "barrel?" from completely closing. I moved things around to where they should be but havn't run it yet to see if it makes any difference.
You are a tremendous help! I greatly appreciate this!
 
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yeah the NGK pn: B6HS, no you don't have to open the CDI to remove the lead it is screwed in, anticlock wise will remove it, clock wise to fit a new lead, you can with a bit of effort and some lube on outside of the lead, screw in a 8mm lead but a good 7mm is enough.
The circlip is suposed to be under the C clip/ pacman washer, needle first, then washer, then spring.
 

racereeves

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Jun 6, 2008
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Ok. I actually asked too soon. I found threads about the wire and spark plug type. It's interesting that the PDF installation instructions has the pac man washer UNDER the c-clip. What a crock! Thanks again
 

racereeves

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Jun 6, 2008
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Just went to the motorcycle shop and got a B5HS plug which, from what I understand, will burn a little hotter than the B6HS. I got a high quality NGK boot and high quality piece of 7 mm wire. This should do the trick. I'm going to set the needle back to where it was during break in (second notch from the end) and bend the float tangs back to where they were originally. Bending the tangs didn't change anything really. We'll see what happens after that. I love to tinker so all of these things are really teaching me a lot about two stroke motors. Thanks for everybody's help:)
 
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