Bogging/ketchup effect

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You have the FgMT right? There is no venting tube. The tube that goes to the bottom is the intake or fuel to carb and the tube that goes to the top is the return tube that returns unused fuel back to the tank. The MT vents with the fuel cap and if its warm out ,and sometime when its not, the tank builds up pressure and you will need to open the tank cap slightly to release the pressure.(You will hear it release if its there)
If you are running the stock exhaust then a new exhaust is the best way to get some more umpf out of the engine.
Is it bogging from take off or when going from mid to high RPM's?
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Is it bogging from the start or from 1/2 throttle to Wide open throttle (WOT)?

Here is a little tuning info to tide you over till we hear about where you are getting your boggin on the low or high side.

I would mix at 25 or 28:1 for the gas (I allways run 28:1). Buy a zen owners manual. CY does not come with a manual but the Zen manual has a lot of good cross over info.

Set the screws per my carb tuning instructions for a rich setting to start, and have a new spark plug or two on hand in case you foul a plug. I would rather foul a plug, than squeek a motor before it is tuned.

Start the engine with the car on a stand with the wheels off the ground and run it for about 5 min, reving it up, but not holding it anywhere for long. After that is done, pull the plug and see if it is getting dark. If it is (and it should be)-- good. let it cool, start it again and run it (driving the car) half throttle for about 10 sec or so (after it is all warmed up again). From half throttle, stop the car at your feet and hit the kill switch. Try to not let it idle or run at a different RPM--stop the engine as quick as you can for these tests or the plug can give you a false reading. If the plug is still dark, your safe to run another test at a little higher RPM. Keep checking the plug between RPM runs as you increase RPM for each run. As long as the plug is still dark, you should be safe. when you get to full throttle and about 10 sec at full throttle, and the plug is still dark, you can lean out the high speed jet 1/8th of a turn at a time and keep doing full throttle runs till the plug is a med brown in color. You may be able to go more lean than that, but a med color is safe, and won't foul easily. Your exhaust gases are now hot enough and the plug retains enough of that heat to burn off deposits so it won't foul a plug easily. A white or light color plug indicates that the exhaust gasses are dangerously high in temp, as the plug retains enough heat and burns off almost all of the deposite (which is why the plug is white in color). If your plug does not gain color with the high out 1.75 or 2 turns out, you have some other problem like bad fuel delivery, or a air leak that must be fixed before you run more, or it might happen again. By the time you get the carb tuned with this method--it is broke in and ready to beat. Break in, IMO, is not as critical as most people think. The Zen owners manual doesn not include a break in procedure, and since it has a lot of other good info, I feel Zen doens not figure it is important either. I highly doubt the japanese company simply forgot to put it in there, and the manual has been updated, still with no break in procedure.

On the stand at first, I start with the low at 1.5 out. If you trun it in, the RPM will go up, and the engine might start buzzing (vibrating noticeably). Set the jet richer than that setting by about 1/4 turn, and leave it there until you get the high speed jet tuned in real conditions. Then you can fiddle with the low speed for better low speed acceleration--but it might be hard to notice because of the clutch engauging at about the RPM where a piped engine comes on the power anyway. On peds, that have no clutch and direct drive (the ped stalls when you stop), we often actually go a bit richer on the low. It seems to help get the engine get up to 8,000 RPM better (where the power usually starts comeng on with a pipe).

The high speed jet is by far more critical to prevent engine failure than the low speed jet---even though both jets flow fuel after about 1/3rd throttle. Adjusting one jet does effect the other a bit because they both flow fuel after about 1/3rd throttle--so keep that in mind. Every engine I have lean seized while learning, and seen other that have seized allways happened at full throttle--or close--and never on a stand with no load.

I know other people may think I am too anal about jetting the carb, but I feel this is the safest way, espically if your new to the engine. HPI and some others just do all the tuning on the stand. They hold it wide open and lean the HS jet till they get top RPM, then they richen the needle after that and run. I know a hot engine (oh yea--allways tune at operating temps) and a engine under load needs more fuel, so I am not sure if I would totally trust the on the stand method of tuning the engine. I would rather use real conditions, and use plug checks. Plus, I really don't want to hold a engine wide open with no load. It will be interesting to see if my end settings match the setting of the stand method though. That is something I will check out this summer. But all other gas two stroke engine for bikes, quads etc--use the spark plug method. I think the other methods are some nitro mentality comeing into effect--but I am not sure.

Use a good foam air filter oil on a foam air filter (can buy the special tacky oil at any dirt bike shop). A special tacky foam filter oil (like Bel-Ray or PJ1 foam filter oil) is tacky so gravity and air flow forces won't let the oil settel to the bottom of the filter, or get sucked into the engine--leaving the filter unprotected in areas. Fully saturate a clean foam filter with the oil, and squeeze out the excess with paper towells. the foam is a "open cell" type of foam that breaths. You don't want to fill the cells with oil and leave it there, you just need to coat the walls of the cells with oil for best air flow, and great dirt protection (water will let dirt pass through a foam air filter though--so try to stay out of the water). Make sure the filter is on correctly (for Baja owners, the baja is a bit tricky--but the stock filter is probably the best one out there IMO.)

If you are using a can for a exhaust system, make sure you have long stingers on it. I have seen X-cans suck in dirt, and fill the engine with sand (believe it or not) that did not have long stingers on it
and you have richened your high end needle and still doing the same thing ? sounds to me like its runnning alittle on the lean side and bogging for fuel , also make sure your pick-up is on the bottom of your tank and not pulled up to far ..
im just pissing in the wind here and guessing
When I hit WOT from full stop the truck start moving no wheelies or anything just starts to accelerate. Then when it hits 1/3 of top speed it explodes and starts to scream and acc rapidly. Im not really sure the right word is bogging. I have tested stock settings on the carb +- 3/4 turn. I can notice the diffrence between to rich and to lean when during my tests. Anyway I have ordered a Wt-813 carb and a reedvalve from Oniell-b maybe it will sovle my "problem". Im also going to get the high RPM spring for the cluch.

From that description, it sounds like the low end needle is adjusted too lean.

No power from the start, but power on the top end.

Do you get gobs of smoke on low end, or hardly any when you nail it?
From that description, it sounds like the low end needle is adjusted too lean.

No power from the start, but power on the top end.

Do you get gobs of smoke on low end, or hardly any when you nail it?

Hardly no smoke. but whan I adjust the low end needle its starts to smoke. Could be the pipe that are causing this effect.

I'm no expert on these engines, but I do some minor tuning of my own.

It seems as if you need to richen the low speed needle just a hair to get more fuel to her when to peg the throttle.

Make one tiny adjustment, then take off and see if it fixes it. If it helped a bit, keep going in that direction tiny turns at a time. If not, turn it back to where you started. Then slighty the other direction and test again until you hit that sweet spot.

But I'd like to hear others chime in first.
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