Help..want to know more about popoff pressure

ISeeWetPeople

ISeeWetPeople

Location
Finland
Lake testing yesterday..

had same pop-off than earlier but i change my jettings to 127,5/130 (had nothing else =) ) at firts it was hard to tune for some reason but then i got it.. not perfect but close.. i think the low end response is good but i thing that it takes just little bit too long to get high speed. its possible to carb that out maybe but i stil think that engine runs little too agressive and it vibrate too hard. i have two new engine mounts but two are old so it could be that too. what do you think can motor vibrate effect to gas flow? i will get new engine mounts next week or so.. then i hope that the vibration will go away=) but cant help to notice that my engine is not running smoothly. or it is just bpipe big carbs msd total loss reeds head that makes it so agressive.. two months ago i had 780engine that blow.. but i think it felt smoother than my 701.. dont know
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
ISeeWetPeople said:
Lake testing yesterday..

had same pop-off than earlier but i change my jettings to 127,5/130 (had nothing else =) ) at firts it was hard to tune for some reason but then i got it.. not perfect but close.. i think the low end response is good but i thing that it takes just little bit too long to get high speed. its possible to carb that out maybe but i stil think that engine runs little too agressive and it vibrate too hard. i have two new engine mounts but two are old so it could be that too. what do you think can motor vibrate effect to gas flow? i will get new engine mounts next week or so.. then i hope that the vibration will go away=) but cant help to notice that my engine is not running smoothly. or it is just bpipe big carbs msd total loss reeds head that makes it so agressive.. two months ago i had 780engine that blow.. but i think it felt smoother than my 701.. dont know
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Excessive vibration can make the needle leak. Running the ski on the trailer with the airbox off can let you see if there is any dripping from the venturi.
 
Fro Diesel

Fro Diesel

creative control
Location
Kzoo
schicks said:
flame arrestor...airbox. stock? how many screens? filters?

less restriction = higher pop off
more restriction (all 3 screens) = lower popoff

i think thats how it goes.
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Backwards broski.

I had to lower my popoff when I put on an aftermarket flame arrestor. Had to increase popoff when I went back to stock.

in the manual you will see a graph of how popoff affects throttle response only to about 1/4 uploadfromtaptalk1406390090502.jpg
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
Fro Diesel said:
Backwards broski.

I had to lower my popoff when I put on an aftermarket flame arrestor. Had to increase popoff when I went back to stock.

in the manual you will see a graph of how popoff affects throttle response only to about 1/4 View attachment 254571
Click to expand...

Group K says... Low 0-35%, popoff 20-50% and high 30-100%, and I find that is much more applicable to my limited experience. I feel that my pop-off changes effected response well past 25%. I suppose my throttle lever could not have linear pull.
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
Vumad said:
Excessive vibration can make the needle leak. Running the ski on the trailer with the airbox off can let you see if there is any dripping from the venturi.
Click to expand...

i think so too..

i read group k guide to adjust carbs and it says there that 90% cases you can adjust your low screw in your trailer when ski is partially submerged.. but i could not notice any difference how my engine was runnid during my adjust.. i turn my low screw 2 1/2 rounds out and no difference at all.?? ill bet that my engine is just vibrating too mutch

any other ideas?
 
speedysprocket

speedysprocket

Alex
Location
Chesapeake, VA
You can stack two or three anti syphon valves on the metering block inside the carb to reduce or eliminate the dribbling at idle. This is the little, clear check valve on the block that covers the jets...
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
why not ask here aswell.. why does my carb closer to coupler spray little oil around outside of the engine? when i take of the flame arrestor there is some oillish stuff inside of the carb . what cause this any ideas?
 
WB1994

WB1994

Location
Amherst NH
Vumad said:
Group K says... Low 0-35%, popoff 20-50% and high 30-100%, and I find that is much more applicable to my limited experience. I feel that my pop-off changes effected response well past 25%. I suppose my throttle lever could not have linear pull.
Click to expand...

Your going to listen to group K over the people who designed and built the carb? What your saying is the needle pops off at 50%.
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
WB1994 said:
Your going to listen to group K over the people who designed and built the carb? What your saying is the needle pops off at 50%.
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No, I don't trust what group k says. What I'm saying is that their explanation seems to be more in line with my experiences. I feel that cruising at 1/2 throttle and 4000rpm and then stabbing it, that a change in popoff can effect this situation.

Mikuni says that the high speed screw is for adjusting wot, but I feel high screw setting changes around half throttle.

I'm not saying group k is right, nor am I saying mikuni is wrong. I'm saying that my personal experience is more like one than the other. poop, I never even suggested I was right. Just the way I felt it happened.
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
speedysprocket said:
Is it white, like oil mixed with water? Your reeds may be getting worn and allowing some of the crank case pressure back up the carb, spraying fuel/oil out with it.
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poop indeed.. sounds that i have to hunt down a new set of reed petals somewhere..

or should i just get v force... some say R&D M-16 reeds are way better than v force.. not so strong tho.. new petal kit cost the same that new v force reeds!!!
 
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