Stock carb mod

[Masterm222]

Both my bikes seem to surge at WOT. They don't seem to rev like they should. I forgot to turn on the fuel once and the bike ran like I had NOS just before it died. What would you suggest? Solder and re-drill the main jet smaller? Shave the piston skirt? I NEED HELP!

by norman
right before it ran out of fuel the bike went leaner that is why it felt like nos. You might need a one size leaner main jet. should also stop the engine surging at wot.

 

[mechanickid]

This should be very easy to fix, raise the clip a notch on your needle (lowering the needle)
if you notice improvement raise the clip again, if the low end bogs bring it back down. check your plug after you get it hot, if its whitish, you need to raise your clip, if its black you need to lower it, if its brownish then its perfect.

 

[ken murphy]

though my troubles never seem to end with these engines,Iv'e found that they do run rich in general,and i have had some limited sucess with the jets & I have solderd them shut and redrilled em,the size I used was .024 pretty small i got my drills at ace,also gey a welding tip cleaner (oxy----acet) so you can measure the size u know double check use nap gas to use the solder & be careful not to melt the jet best thing to do is get a differant carb delorto is a goo choice. Good luck ------Hppy trails!

 

[Egor]

MasterM Your experiment was correct for finding what it is that is wrong with your engine. That is exactly what I would have done. Your engine is fat lowering the needle will help the mid range, but the main jet is for full throttle. You can also lower the float level, (the same thing you did by shutting off the fuel). By bending the tabs slightly down to shut off the fuel in the bowl sooner. This will simulate the condition you made by shutting off the fuel, this is also a one of the methods used to tune the carb, they are supposed to be closer from the factory. Have fun, Dave

 

[Masterm222]

I soldered and redrilled the main jet smaller (size? smallest drill bit I own!) and lowered the float level. I installed the carb on the motor I got from Gasbike and now it doesn't surge, it reaches a steady 20mph (same top speed) and vibrates a lot! I swapped carbs with my other bike and top speed went from 25mph (44t sprocket) to 30! Made some WOT runs going to check my plug this morning. Suppose the fuel is foaming due to exessive vibs on the Gasbike motor? Motor is rubber mounted to save my ass and hands. Allowing the motor to vibrate more? Just thinking and looking for a solution!

 

[DIYMark]

Best thing would be to true to crank lol - and possibly balance.

On my new motor I chucked the crank in the lathe and dam it was out of true! 1.2mm axially and 1.1mm radially! Not to mention the bolt on counter weights. So What I did was true it all up and my motor runs awesome now. I didnt balance because in the counter weights the cut out looks exactly the same as the ones in Jims computer simulation so I left it at that and did not balance my motor. This happend to be the cheapest motor I could buy and it was better overall than the 100 dollar more one I got last time lol!

 

[joe-craft]

hi just an odd question i have a pk-80 limited kit, my main jet got some grud lodged in it and i took a #60 drill bit to clean it out, and i guess it was way too big, and now its not working the way id did before, so i was wondering what the stock jet size was. if someonje could tell me thats be great.

 

[ken murphy]

Your .012-.015 thousands oversize.With a#60 drill------#72 is what u want that will put you at .026 and it will run out good so be careful and clean it up get some flux and solder and with napp gas at low heat solder the hole shut and redrill be creful not to melt the brass and pay close attention to your overall lenth as the needle comes in contact with the jet. (the top of the jet).Good luck and happy trails.

 

[joe-craft]

okay thanks alot, another question any one try to but the carb kit from spooky tooth, i keep trying but when the shipping method come up there is nothing there, idk if its that he doesnt ship to canada or what. anyone else have this problem. oh and another question, when buying a racing carb that is for a pcoket bike what size should i get, oh and what size spark plug should i use?

 

[ken murphy]

still cant find a piston Roland is sending the old one back----so "im going to try to put that one back,after I clean it up!I'm going to lay it out and get the exact meassurements from the wrist pin down to the bottom of the skirt of the piston. before I put it back.-----this piston thing is getting old!

 

[Egor]

What is happening with the piston you are getting? Dax has the long rod pistons and I got a short rod piston from Kings motorbikes Kmotorizedbikes.com But I can't insure that they have not changed vender's and now have something completely different.

still cant find a piston Roland is sending the old one back----so "im going to try to put that one back,after I clean it up!I'm going to lay it out and get the exact meassurements from the wrist pin down to the bottom of the skirt of the piston. before I put it back.-----this piston thing is getting old!

 

[jak stoll]

yep I been through the same thing bro
I was able to clean up the piston I had for the time being & it has been great for almost a year now
take care
JAK

 

[ken murphy]

got stopped by the cops last night for the first time my friend & i were ridin and they pulled us over and said we had to ride on the sidewalk only-------thats not what the law says!no tickets we had lights, found out we can regester the bikes
-------dont know if I will---------
happy trails
Murf

 

[Masterm222]

Need a little help. I can't seem to get the needle and seat to seal. Clean and adjust as much as I want and the fuel level is always above the level of the gasket. Faulty seat or needle? Tried a brand new carb and same thing. Solution, new mukini 18mm carb? Could this be caused by engine vibration? I could hose mount the carb to eliminate some vibration. This motor seems to run reasonably smooth but I suppose it is still possible. Anyone go through this problem before? HELP!

 

[ken murphy]

when u have the carb off make sure when the bowl is off with the carb upsidedown look at the needle and see if its seating, you are talking about flooding correct?------Are you saying that you bike is flooding?-------fuel flow? You can slitely bend the tangs to adjust your float. the carbs arn't the best but they do work-----but the can sure flusrate you.You are talking about the fuel inlet aren't you?----if not explain futher-----good luk & happy trails

 

[Masterm222]

I have bent the tangs to lower the float level. No luck. I thought maybe the float was sinking although it had no fuel in it like it was so I changed carbs. Now I have a new needle and seat and a new float. No luck. Still after a short ride if I loosen the two screws that hold the bowl gas runs out like it was full to the top! The only way I can get over 25mph is to limit fuel flow by almost shutting off the valve at the gas tank. (not a good way to solve this problem!)

 

[Masterm222]

How I discovered this problem is I am trying to get this bike to keep up with my other. I have changed jets between the two. Tried smaller and larger main jets. Swapped mufflers. Expansion pipe. Slant plug head. Different spark plugs and gaps. And every combination of. This bike right now with my latest combination will get to 25mph in 5-6 seconds but then slow to 23. The bike on the right in the picture will take its time to get to 22 (I will work on that next) but then will sing right up to 34

 

[Egor]

Master I find it hard to believe that you have two carbs that are the same, but it is possible. They are very poor at production and when they get something bad I guess the just keep going. I have had some luck with lapping the seat in on some metal sets. What you do is take an old yellow pencil and cut it down till it will just stick out of your drill chuck, next take some course tooth past and put it on the end of the needle and place in the seat, next use the drill with the pencil and with the eraser as friction get it to turn the needle, do it till you see a clean line around the end and it should seal fine. Let us know how it works. I also keep all the rubber ended needles I find and put them in where they fit. Have fun, Dave

PS: Comet and some lite oil makes a good grind paste also.

 

[Masterm222]

EGOR, I also have a hard time believing I could have two bad carbs. I am going to try the method you described tomorrow. I wish I had a rubber tipped needle to try. I do have comet and toothpaste though! What a ride on my flame job bike today. I was playing with needle clip settings today and while riding home from Harbor Freight (new dremel for aid in shift kit install) I hit 37.2mph on the flat. Bad dead spot around 19 to 22 about half of the time but after that it gets up and goes. I figure the bike with the carb problems has such good low end power but no top end really needs more than one gear! Then maybe it can keep up! What am I going to do when I have my Giant Stiletto chopper built and running?! Then I will have three to tinker with!

 

[Masterm222]

I can't thank you enough Egor! After I lapped the needle in I had to raise the float back up because it seemed to run out of gas after a block of WOT. Now it accelerates smooth and strong up to 32mph. I have good low end powerloads of midrange and a high enough top end to keep me smiling. This bike is ready for the shift kit now! Thanks again!