bog down at top speed

You can always put it back to number 4 if it won't idle...I say go for it.

remember to judge the iddle and accel after the motor is hot.

I regret that I don't have any Pics, but it seems you figured it out, Brandon. Good Deal!! Glad I was able to help.

I still have mine set at the 4th (lowest groove) at this point. And I have found an odd thing happen while still set there. I'll explain...

When I first start the engine, the idle seems WAY to high. Like it's still to Lean? This doesn't make any sense to me and I'm still trying to understand it but... Hmm.

I'm going with Joe's post too. If it Absolutely will not idle properly, I'll re set the jet to the 3rd slot. At this point in my trials I've just been re setting the idle screw when first starting it up to lower the idle speed. (back it out)

BUT! Also read and recall Echo's post about the engine temp. The other half of my new Odd behavior is that after the engine warms up I have to turn the idle screw back in again to keep it from stalling out when I let off the throttle.

I will keep trying it 'as' is for a while, cause resetting the idle screw can easily been done while still on a ride. When I Start, I can back it off, and after a warm up I can set it up again.
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Now for my personal observations that agree with Brandon about resetting the jet in the carb. How about that throttle response, huh? WOW, what a difference!! The bike takes off more Smoothly, hits a higher top end speed, and there ain't no more Bogging, eh?

I'm still in my Trials on this one, and have yet to take her out on a long haul (5+ Mile WOT ride) to Confirm, but in the little Neighborhood Rides we've (Jim & I) taken have Proven the increase from 22 MPH steady up to a good 28 + Steady Speed!!! In fact, I had a good and sustained 30 MPH Confirmed Top End for a stretch of road that used to yield a mere 22 - 24 MPH just this evening.

Maybe not a whole lot when looking at Numbers, but it sure was a Heck of an improvement when on the Ride!

What is the root cause to high end power loss and why did it start to occur? I have about 100 miles on my motor and I too have developed the same problem, at WOT I'll cruise at about 20mph then the hand of God will come surge me up to 28mph then I'll lose that power then the hand will come back. I think there is a silver bullet to this problem and riders with this problem have not found it. I will try all the variables one at a time so I can pin point the solution. The first thing I did was take the stock plug out, it was brownish. I ran it at .020 (no hand of God less power), .030 same, .035 (hand of God), .040 (hand of god same as .035) .045(same) .050(same). So "normal" operation started at .035. I had it originally at .040 and will set it there for future tests.

BTW riders with WOT power surge, did your problem develop or was it always there?

Mine bogs at WOT as well. Kinda annoying. But only WOT above a certain RPM. I can be cruising along at nearly full throttle, then if I go WOT I actually loose speed! But going up hill at WOT it doesn't surge.

I'm thinking it has something to do with the gas being all frothed up in the bowl from vibration at high RPM. So the jet can't get enough fuel. I have put some thought to it today, and I'm wondering if raising the float would help.

I'll give that a try later tonight or tomorrow, and report back.

BigDream,

My issue developed over time. And guess what.... ? It's back. Dag Nab it!

Now that Chrisme has posted, I wonder it that may be a part of the issue too. I may have to look into the Float's level I guess. The Fuel line still seems full, but that Bog Down is back again.

Only now, I bog out at 28 MPH, instead of the previous 22 MPH. ~~~~~

So... The Rejet helped, but it wasn't the Long Term Solution that I once thought it was. Bummer. And for what it's worth, I now have 300+ Miles on the bike.

I really want to get this sorted out. Not that I will ride it that fast to often, but it is just the feeling that it isn't tuned as well as it could be that is annoying me. Ever since I put hose between the engine mounts and the bike I have had very little vibration, but this is still holding me up in terms of top speed.
If it does have something to do with vibration I'll mount the carb on a flexible hose connected to the frame. That might help reduce vibration in the carb.

Hi Guys,

Just came across this thread and couldn't help but notice I had the same problem when I first took my bike out. I went about four laps around the block and it would bog out then speed up.
It seems when I let off on the throttle it would smooth out but when I would attempt to open her up again the problem returned.

It started to drive me nuts so obviously I looked to the carb and WA LA!

First I checked the line and tank filter and they weren't plugged so then I took the "CARB BOWL DRAIN SCREW" out and the gas didn't even run out. I could see something in the screw hole that didn't look like it belonged there so I took a pair of tweezers and pulled it out and then the gas came running out along with a bunch of other garbage.
It all ran out into a rag and upon examination it looked to me to be paint chips from the tank.

This was kinda odd I thought because when I bought the engine the first thing I did was put a little gas in the tank and swish it around to get any crude out of it so something like this wouldn't happened and also to check for leaks.

Anyways that cured my problem and was a simple fix. Hope this helps somebody out.

RPM

I will try the float bowl next. There could be paint chips/rust, vibration and perhaps water condensate that can float on top of the fuel in the bowl. I've been told that when water wicks in, it can cause some power loss and it can cause this problem for a long time. We should all drain our floats and report back. Good Luck.

today I took off my float bowl. It was clean, and my jet isn't clogged. Put it back together and still bogging. GRRR.
But now that you mention the paint chips thing, I didn't check the inlet into the bowl. Maybe there is something stuck in it restricting fuel.

i might be jumping in here a little late . but if your motor is bogging down at full throttle . and if it picks up if you let the throttle back just a little , then that means too much air not enough gas . you may have a leak somewhere in the system.

All of the bogging at WOT problems here sound like a case of the main jet being too small.

There is a taper on the needle that is the "metering system" so to speak. If the bike pulls well everywhere but WOT at higher speeds, then the chances are the jet is too small.

The cure is a bigger jet, and then move the C clip to a leaner position.

I dropped the bowl last night, two screws and the bowl drops down. There was a 1/16th of an inch of very fine rust granuals in the bottom of the bowl. I cleaned this out, cleaned my in tank fuel filter, and added an inline filter specified for air cooled 2 stroke engines from Autozone in the lawn mower section. My test ride still had the same problem at WOT. So starting from stock specs, I know it is not plug gap or contaminates in the bowl. Next I will add thicker rubber mounts to reduce vibration and possible fuel frothing. Right now there are inner tube mounts, I will move up to coolent hose rubber and take a test ride. Then I will fill the tubular frame with Great Stuff Expanding foam and take another test ride. I'll report back with the results.

FIXED IT!!!
Vibration was causing the choke to fall down restricting airflow at high RPM at WOT. Zip tied the choke off and now it runs mint!
I also dropped the float which got me a bit more top end speed, but the choke is what really did it.

If you take the air cleaner off you'll see there's a nut on the inside of the choke lever. You can tighten it to make the choke arm stiffer.

Junster said:

If you take the air cleaner off you'll see there's a nut on the inside of the choke lever. You can tighten it to make the choke arm stiffer.

Click to expand...

Yea, I know... I have since done that. But it was easier to just throw on a zip tie and go. I was to excited in finding what was wrong... Now my bike goes without any bogging at all. So nice.

Way to go Chrisme! Glad you figured it out.

Often times than not we look for a more complex solution when a simpler rectifies the problem.

The danger is getting ahead of ourselves by not taking the time to do a thorough diagnostic starting with the basics and instead jumping to conclusions then possibly covering up the condition or even making it worst by screwing something else up which needn't be done in the first place.

I'm speaking from experience here and the money out of my pocket to back it up.

The inlet into the carb bowl was a good idea even though everything checked out. I believe most people wouldn't have went to that extent simply thinking its ok when in actuality maybe its not.

Thats the difference between someone being thorough and not. In your case you solved the problem by simple observation and who would of ever thought of suggesting that.

Thumbs up!

RPM

I've been closing down the petcock- a crude method, but it seems to work-

So the problem then seems - too much gas, (or too rich) - too much gas to air when it really gets sucking

I drilled four or five holes in the plasic air cleaner- Better air flow seems to help, and I don't ride in dirt or rain

I'm going to play with mixture now- start real oily. An oily would be better for the motor's long life, and it may even run better

It always runs best under load, and then this same bog down, reported again and again-

a 36 and some smoother narrower tires have helped- my cruise speed is much higher now and pretty decent without opening the throttle all the way-

and it's much less noisy before that 2 stroke whine really winds up!

I was almost mad at myself when I found out it was the stupid choke... I made sure the jet, the tickle, the air vent to the filter, and the fuel inlet weren't clogged. I spent almost 2 hours playing with different float levels, different positions on the clip... and NOTHING. The I revved it at idle and saw the choke handle move...

I think part of the diagnostic problem here is some are experiencing a "bog" because of an over rich condition, ans some are experiencing a "bog" due to fuel starvation at higher rpm.

Guess it depends on which kind of "bog" or your description of the "bog".

Long distance diagnostics are a biotch.