Modified Stage 2 Predator 212 Hard to Pull Start and Mikuni 22mm Running Rich

delray

delray

Well-Known Member
#41
#41
JackJ217 said:
My cam is rated for 7500+ but I’ve seen it go well over 8000, and the juggernaut says it’s good for up to 8500+
Click to expand...
think your misleading people here when you say your cam is good to 7500+ and up to 8000. no way that cam is still pulling power at those rpm's. power band at that rpm would start to drop off. maybe with a set of 1.3 ratio rockers and some good head work and correct carb...etc.. also mentioned earlier that you only gotten to turn 4480?
you also said something about gas dripping from the intake. is your float set correct? and or carb mounted level? just things to double check and rule out for problems.....:scooter:
 
H

Havasu Dave

Moderator
#42
#42
You've got your carburetor tuning issues causing your problems. The "needle" that is attached to your throttle slide does nothing until you're at about 1/4 throttle. It does not affect how the engine starts. That is handled by the fixed jet in the bowl, and is smoothed out by the air bleed screw- which really doesn't prevent it from starting either.

Studemann had it right in his first post, raising that needle causes the engine to run more RICH, more quickly. You also said it right, because you said "raising the clip" which means "lowering the needle." The needle is sitting in the main jet hole, almost blocking fuel from going through it. As the throttle is applied, the needle lifts out of the hole. This allows more fuel to flow through that main jet. The needle does most of the "tuning" from about 1/4 to 3/4 throttle, but at wide open throttle, the needle is completely out of the hole and it's all main jet.

Your problem right now is not your needle, because it has no effect on starting the engine. Adjusting that needle is only done once the engine is starting correctly, and once you know you can achieve wide open throttle under load. (Never run these at WOT without a load)

Since you had fuel running into your intake manifold, it means you seriously flooded the intake by repeatedly trying to start the engine, and/or your float is not adjusted to 24-26mm, or the float needle seat is leaking. Again, Studemann probably called it right- that excess fuel is hydro-locking the piston. If the float is set too low, (you set the height with the carb upside down,) the bowl will over fill with fuel, sending raw fuel into your intake.

I highly recommend reading Ian Williams Tuning article on Mikuni tuning. It's an easy read and explains the concept of operation of these carburetors as plainly as I've seen. Once I grasped the concepts there, I found that tuning these carburetors was very simple, but you have to take it one circuit at a time.

One final note here, is that plugs can become fuel soaked and stop working, even after drying out. Take nothing for granted.
 
J

JackJ217

Member
#43
#43
delray said:
think your misleading people here when you say your cam is good to 7500+ and up to 8000. no way that cam is still pulling power at those rpm's. power band at that rpm would start to drop off. maybe with a set of 1.3 ratio rockers and some good head work and correct carb...etc.. also mentioned earlier that you only gotten to turn 4480?
you also said something about gas dripping from the intake. is your float set correct? and or carb mounted level? just things to double check and rule out for problems.....:scooter:
Click to expand...
I'm just saying what the specs are on my cam. My torque converter is limiting my engine from revving higher, I can feel the power dropping off once I get to about 4000 rpm's. Isn't gas supposed to go to the carb? That means that it has to go through the intake manifold in order to get there, and my gasket was completely shredded, causing gas to leak. I've tried to get my carb level and as far as I'm know it definitely is.The gas leak wasn't from where the carb mounts to the manifold, it's where the manifold mounts to the head. What do you mean by "setting the float?" As I said I'm very new to Mikuni carbs.
 
Last edited:
delray

delray

Well-Known Member
#44
#44
for tuning the carb. best thing you can do is just read article that dave had posted above. it's very easy to understand for beginners and should put you down the right path.....:scooter:
juggernaut will be the ticket in helping you motor spin some rpm's.but you will need also to install a larger rear sprocket. if you want that heavy bike to come out of the hole quicker and turn some real rpm's. otherwise it my take some distance to make that bike to move out good. trail riding it? bigger sprocket. i believe gopowersports sells bolt on sprockets for your bike.
hopefully they got the juggernaut problems also figured out. less than 3hrs running time on my unit and it was done and that was with a mild built tecumseh behind it. i hate to see a built clone can do...
https://www.oldminibikes.com/forum/index.php?threads/340-salsbury-series.168096/page-5#post-1246291
 
Last edited:
J

JackJ217

Member
#45
#45
delray said:
for tuning the carb. best thing you can do is just read article that dave had posted above. it's very easy to understand for beginners and should put you down the right path.....:scooter:
juggernaut will be the ticket in helping you motor spin some rpm's.but you will need also to install a larger rear sprocket. if you want that heavy bike to come out of the hole quicker and turn some real rpm's. otherwise it my take some distance to make that bike to move out good. trail riding it? bigger sprocket. i believe gopowersports sells bolt on sprockets for your bike.
hopefully they got the juggernaut problems also figured out. less than 3hrs running time on my unit and it was down and that was with a mild built tecumseh behind it. i hate to see a built clone can do...
https://www.oldminibikes.com/forum/index.php?threads/340-salsbury-series.168096/page-5#post-1246291
Click to expand...
Alright. I was already thinking about maybe going with a 60 tooth? I don’t want to lose too much top end though. My bike came with a 50 tooth
 
SAS289

SAS289

Well-Known Member
#46
#46
JackJ217 said:
Alright. I was already thinking about maybe going with a 60 tooth? I don’t want to lose too much top end though. My bike came with a 50 tooth
Click to expand...
You won't lose top end with a 60 tooth because you will have a higher RPM and more power to drive the load at top speed. Others have experienced top speed gains by gearing in that direction with less of an engine that you will have once your issues are fixed. If I had your engine mods and chose a Juggernaut I would use 9 tooth and 60 tooth gearing to start with. In fact, I will be gearing my bike this way without a Juggernaut and "hot" cam on my governed engine with a TAV attached. The specific 60 tooth I want is currently out of stock. My 9 tooth is already installed.
 
J

JackJ217

Member
#47
#47
SAS289 said:
You won't lose top end with a 60 tooth because you will have a higher RPM and more power to drive the load at top speed. Others have experienced top speed gains by gearing in that direction with less of an engine that you will have once your issues are fixed. If I had your engine mods and chose a Juggernaut I would use 9 tooth and 60 tooth gearing to start with. In fact, I will be gearing my bike this way without a Juggernaut and "hot" cam on my governed engine with a TAV attached. The specific 60 tooth I want is currently out of stock. My 9 tooth is already installed.
Click to expand...
I have a 9 tooth but i am currently using #40 chain. I can't find any #40 sprockets on gopowersports tho
 
SAS289

SAS289

Well-Known Member
#48
#48
JackJ217 said:
I have a 9 tooth but i am currently using #40 chain. I can't find any #40 sprockets on gopowersports tho
Click to expand...
I wouldn't get it from GPS. I would get it from OldMiniBikes. Read the description of the part. If I didn't hate the look of the solid sprocket I would have already got this one.

This won't take the link properly.
 
Last edited:
MiniBikeDan1980

MiniBikeDan1980

Active Member
#49
#49
I agree with member SAS289, buy your parts from OldMiniBikes instead of Go Power Sports. Go Power Sports has given me nothing but problems & I stopped doing business with them years ago because out of the three orders I made they messed up all of them & they cost me money because of there own mistakes.
 
J

JackJ217

Member
#51
#51
MiniBikeDan1980 said:
I agree with member SAS289, buy your parts from OldMiniBikes instead of Go Power Sports. Go Power Sports has given me nothing but problems & I stopped doing business with them years ago because out of the three orders I made they messed up all of them & they cost me money because of there own mistakes.
Click to expand...
I’ve only had ever had one “problem” with them, but it was mostly my fault. I misunderstood that the straight Mikuni throttle cable would only work on a go kart, but even though it was mainly my fault they still sent me the correct cable in two days. I’ve placed 7 orders with them with since December 2019 with over $700 spent so one slight mess-up is no big deal. As far as I can tell they’re pretty good people to do business with.
 
J

JackJ217

Member
#52
#52
Alright guys I’m leaving tomorrow to go camping and there’s no reception anywhere up there so hopefully my parts are here when I’m back. (sadly no mini bikes allowed because it’s state property or I would have waited until my parts arrrived) This forum is a life saver lol
 
J

JackJ217

Member
#58
#58
I just found 16 1 star reviews for OldMiniBikes saying that they have bad packaging, slow shipping, they don't even ship some orders, and some parts are broken and can't be returned. Should I be worried? The tracking for my sprocket says it should be here tomorrow. (BTW we got kicked out of our camping spot because apparently we were "too close to the creek":rolleyes: I've camped there every year since I was like 4 and my dad has since the 80's and it's never been an issue.):mad::mad:
 
J

JackJ217

Member
#59
#59
I got the gaskets, and my engine is still recoiling the pull cord when I pull it, even if I turn it past the compression stroke first. I really have no idea what to do now. I put a new valve cover gasket on because the old one was a bit beat up and there was some oil on it, as well as the metal it rests on. That still didn't help. I pulled off the head and the piston looks fine and there were no extra fluids up there. However there was some oil on the head heat shield, enough that it was starting to mess up the gas/oil resistant paint I put on it. Does anybody have any clue of what's going on? Also my sprocket came, and the mounting holes weren't exactly in the right spots to fit my wheel so I drilled new holes and it works fine.
 
ole4

ole4

#60
#60
do you have a dial indicator? Or good eyesight? you can check for correct operation of the CR. If you have a compression tester that will also tell you if it is working. I am assuming that you have exhaust lash set correctly. There have been multiple threads here on this very subject and in all of them the OP was not adjusting the lash on the base circle of the cam instead adjusting lash on the CR lobe. In your case it maybe the CR is broken. Let us know if you have any of the above three items and we can debug from there.
 
You must log in or register to reply here.
Top