WOT bogging By jeepsteve92xj (Read 1,842 times)

[jeepsteve92xj]

I have been riding my new used Znen and twice during long-ish (1/2 to 3/4 miles maybe) stretches of WOT the scoot will start to bog, but if I let off the throttle a bit and wait, it will pick up and then bee fine for a while.

I'm sure its due and I will replace the fuel filter soon.

But since it recovers, I don't this is caused by the fuel filter.
The ZN150T-F has a low mounted gas tank and a fuel pump.

I wonder if these pumps have trouble keeping up for long WOT?

And any suggestions on a good jet combination for the Znen with a long intake route and a muffler with a small outlet?

[JR]

There are several things that could cause this and since you've already mentioned that you've changed hoses and such it's till very important to make absolutely sure you have no vacuum leaks around the carb and intake mainfold. If they are there they can hurt the pumping capability of the fuel pump especially at WOT.

Also you may need to adjust the carb a touch and even wioth a new scooter sometimes one has the clean the carb especially the high speed jet.

I know Alley will see this soon and chime in, he is the carb guru and has helped many a rider solve the bogs!

JR

[alleyoop]

Yep you are running LEAN You can try Riching up the Fuel Ratio turn it 1/2 turn counter clockwise and see if that helps. If not then you will need the NEXT bigger Main Jet, but if it was running fine before then the Fuel Ratio should be enough. It is probably caused by temp change and your valves are a little tight.
Alleyoop

[jeepsteve92xj]

this Znen is my newer scoot, which I've had for 2.5 weeks.
The valve cover is well buried in the frame, but I do need to check and adjust the valves too.
Haven't opened the carb yet so no idea what jets are installed.

I need to get the washer dimensions for the slider needle for the carb on the Xingyue.

Can't wait til EFI is cheaper and standard!

[jct842]

My 150 I believe is a 150t-f and is a znen did the same thing when new. I cured it with a better vacuum fuel pump. I got it from a mail order snowmobile dealer in wisc. it would run wot for a few seconds then run out of fuel. back off a little then it was ok, crank on it and real quick it was out of fuel. john

[jeepsteve92xj]

Mar 21, 2012 23:05:07 GMT -6 @jct842 said:

My 150 I believe is a 150t-f and is a znen did the same thing when new. I cured it with a better vacuum fuel pump. I got it from a mail order snowmobile dealer in wisc. it would run wot for a few seconds then run out of fuel. back off a little then it was ok, crank on it and real quick it was out of fuel. john

Nice. Pretty much exactly my thoughts, though I back off and it still has enough momentum to refire.
Any idea where or what model pump?

You can see the pictures of my Znen in my signiture url

[alleyoop]

Here you go:
Alleyoop
.aircraftspruce.com/catalog/eppages/mikunifuelpump1.php" rel="nofollow" target="_blank">.aircraftspruce.com/catalog/eppages/mikunifuelpump1.php

[jct842]

That's the one I got. I put it in and it was instantly cured. I Think mine may have been a buck or two cheaper as it was some sort of a special deal then. I buy metal from aircraft spruce for my shop and they are great to deal with too.

MIKUNI SINGLE FUEL PUMP 07-00777 $21.75

[jeepsteve92xj]

Excellent.
This Znen is the first scooter I've had with a pump.

I'll have to order that and get a few more things done and see how it goes from there.

Steve

[sprocket]

I really like those pumps the diaphragms are replaceable and easy to find...

[jeepsteve92xj]

Ordered one off of Amazon, just a tad less dollars, plus no tax and no shipping cost.

Has anyone found a better slider/roller weight for this Znen? I'd like to pick up a little top speed. I am not even sure how accurate the speedo is yet, I'll have to grab the GPS.

Steve

[JR]

You'll need to open up the cvt cover and get your rollers out and weigh them. The Chinese are notorious for putting different weights in and you just don't know without weighing them.

Just for argument sake lets say they are 14g. For a little more top end and good pulling power up those old hills I would drop a set of 13g sliders in place of the rollers. Also if you have a 835-20-30 belt go to a 842-20-30 and that'll give you a touch of top end too.

JR

[imnts2]

What is your tack reading at WOT. I would be inclined to want neat 7000 RPM to get top power. If she is below that , you may actually be gerared a little high, I also like to try just a little larger main jet or lift the needle on notch. That will affect the the top end mixture more than the battom and give you just a little richer which most engines like. It is a lot cooler and safer than even slightly lean.

lefty2

[jeepsteve92xj]

I've ordered a small scale so i can measure what I've got.
I have a lawnmower tachometer + hour meter unit coming because the Znen has no tach. I'm not sure the tach on the Xingyue is accurate so I'll use another tach/hour meter on that one too.
I've read that the Znen comes with heavy rollers. But I forget which group I saw it on and it seems someone threw out 17g as a possibility.

My Xingyue has a spacer needle that I haven't got washers for - came with none and I'll have to pull it out and go to the hardware store.
I have not opened the Znen carb at all yet. I did receive the Mikuni fuel pump to install later this week if the weather holds up.

Two more small questions come to mind:
I know the rollers can get flat spotted but is there any other pluses for siders over rollers?

The drive cover paper gasket - I scraped the Xingyue mating surfaces clean and skipped cutting a new gasket, while the Znen gasket is mostly still stuck in place in bits on both halves. Is it really needed?

Steve

[alleyoop]

Well I got to tell you on the bogging if you backed off a little on the throttle and it speeded up again, it is not the Fuel Pump. All you needed to do is richen up the Fuel Ratio and it would be all right. It is just running a little lean on the top end and usually is caused by TEMP change. But once you richen it up a little it will be find for almost all temps. Remember in HOT weather they will loose some power and to get some of it back you Lean the Mixture. In Colder weather around 60 and below the motor needs more fuel so you Richen the Mixture.

But putting on the Good fuel pump is good but it still might not fix the bogging if the mixture is a little off. The pump will fix the problem if the bowl is not filling up fast enough to keep up with the demand leaveing the Jets uncovered of fuel.
Alleyoop