fuel petcock flow

[niko]

I do not have the original tank and then a different petcock. It's a 125 dtmx petcock!
I feel like it flows well but actually the 125 dtmx was smaller and less powerful!

I timed the flow to 1 liter: 2min10sec

it looks good but can be just a little limit?

can test your flow and timed like me to compare?

 

[HoughMade]

Doesn't matter what other XS400s flow. Think of it this way. Is there any way on earth that with wide open throttle your engine could use a liter in 2 min 10 sec? No way. Your flow is sufficient.

 

[bcware]

Good point! Perhaps check how far the float needles are opening. It can be adjusted; too much and they get stuck, too little and you'll starve the fuel. They don't need to open very much in my experience, so it may be unlikely to be the problem, but it could be worth a check.

Do you have screens on the float needle seats? Are they clogged?

Personally, I think your problem is too uniform through the gears to be fuel starvation.

 

[niko]

Perhaps check how far the float needles are opening.It can be adjusted

how adjust the float needles?

Personally, I think your problem is too uniform through the gears to be fuel starvation.

for me it's strange the rpm problem change on load and i think only a problem of fuel may correspond to the symptom load. don't you think?

you understand what i want to say by "load"? I just want to say: when the bike need power, not only when the bike is static

 

[bcware]

I have another idea; perhaps your ignition advance unit is not working well? I have heard of the springs wearing out. It looks something like this: http://www.mikesxs.net/product/14-0651.html

I am also attaching a photo that shows how to adjust the float needles on my '78.

 

[niko]

tks bcware,

I have another idea; perhaps your ignition advance unit is not working well? I have heard of the springs wearing out. It looks something like this: http://www.mikesxs.net/product/14-0651.html

I don't believe because i 've changed them and now my ignition advance is good (verified with the strobe lamp) and the full advance is about 3000 rpm. And my problem is not always at the same rpm in what gear the bike is

 

[226dark]

good suggestion bc with the timing ATU, i think even before springs will go bad it will just tend to stick in place until reaches rpm's and unsticks. But the problem sounds closer to float levels needing adjustment, possibly

 

[niko]

Yesterday I tried without petcock, just directly with a pipe, and same problem.

 

[226dark]

Doesn't matter what other XS400s flow. Think of it this way. Is there any way on earth that with wide open throttle your engine could use a liter in 2 min 10 sec? No way. Your flow is sufficient.

Petcock or no, that won't change the level of the floats