Change crank to a 3/4 or Engine ?

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LIVIT

Well-Known Member
#1
#1
I recently purchased a nice used 2020 200U-EX, has stage 1 upgrade. Owner gave me a really good deal, because he said the engine was a dog from the start and did not see much improvement at all with the stage 1. I did some carb adjusting, throttle screw etc.. it still was slow off the line and would pop at higher rpm's. Found out why, the valve lashes were way off. Intake was 0 and exhaust was 1. I went ahead and changed the springs to 18lb and set them to .002 intake and .003 exhaust. Big difference but it still lags some and has a bit of pop still at higher rpm. I'm putting a CVT on it tomorrow after my riser plate gets here. But I doubt it's going to still be what I'm looking for. I'm not looking to build a racing machine. But I do need it too have a lot more torque.

I was looking at changing cam, billet fly wheel and rod. Want to change the Crank to a 3/4 shaft. What all is involved in doing that ? Am I just better off getting a 212 and going from there ?
 

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L

LIVIT

Well-Known Member
#3
#3
2old2care said:
Pop from burnt valve, because of tight lash?
What jet was put in with the "stage 1" ?
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Not sure of jet size, it's the one that GPS includes in their stage one kit. I was wondering if maybe that intake lash being so tight from factory had done valve damage. The popping at higher rpm did decrease some after I set the lash. I'm going to open up the lash on the intake a bit more today and see what happens. I am seriously considering just buying a Till 212 and going from there. Considering how nice of shape the rest of the bike is and the deal I got on it. No biggie if the engine is bad. Previous owner was honest about the fact that something was not right with the engine.
 
2old2care

2old2care

Active Member
#4
#4
Well, that's the thing with these - If something like a burnt valve shows up, you might just as well put in a new engine.
At least all the GPS parts will swap over, and you'll be starting with a 3/4" crank, so that makes a torque converter easier.

I just got a Harbor Freight ad saying the Predator 212's were on sale :~) Maybe now is the time .........

Be sure to check the valve lash on the new engine, after break in.
 
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SAS289

SAS289

Well-Known Member
#5
#5
The crankshaft swap is fairly easy. Flywheel removal, side cover removal, and rod bolts. The rod bolt torque spec is 108 inch pounds.

New engine or not is a tough call that you will have to decide. If I were in your position with one bike and it's engine I would figure out what power goodies to use and do the crankshaft during the build of the engine on hand.

I have an extra 3/4" crank and was thinking about swapping it into my stock bikes 196. But I'm afraid to open it because I just couldn't put it back together without including a new cam. That may snowball into "Might as well get a rod for it while it's open", then "Might as well put on some Champion rockers". haha. Next thing you know I have $200 in parts that I don't really need in the engine. But it sure sounds like fun.
 
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LIVIT

Well-Known Member
#6
#6
2old2care said:
Well, that's the thing with these - If something like a burnt valve shows up, you might just as well put in a new engine.
At least all the GPS parts will swap over, and you'll be starting with a 3/4" crank, so that makes a torque converter easier.

I just got a Harbor Freight ad saying the Predator 212's were on sale :~) Maybe now is the time .........

Be sure to check the valve lash on the new engine, after break in.
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Those predators are good deals for sure. But if I'm going to buy a new engine, it's going too be a Ducar or Tillitson. I adjusted the intake valve lash again a bit more open. It still lags at start, but yet again a bit better, picks up speed good once it starts rolling, then it acts like its being fuel starved. Similar to a governor but more of a hesitation pop. I'm putting a CVT on it tomorrow, will see what happens then, tks !
 
Strigoi

Strigoi

#7
#7
If you plan on swapping a billet rod into the engine you'll need to remove the crank anyway. Might as well just pick up a 3/4" crank and put it in that case when doing that.
 
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LIVIT

Well-Known Member
#8
#8
SAS289 said:
The crankshaft swap is fairly easy. Flywheel removal, side cover removal, and rod bolts. The rod bolt torque spec is 108 inch pounds.

New engine or not is a tough call that you will have to decide. If I were in your position with one bike and it's engine I would figure out what power goodies to use and do the crankshaft during the build of the engine on hand.

I have an extra 3/4" crank and was thinking about swapping it into my stock bikes 196. But I'm afraid to open it because I just couldn't put it back together without including a new cam. That may snowball into "Might as well get a rod for it while it's open", then "Might as well put on some Champion rockers". haha. Next thing you know I have $200 in parts that I don't really need in the engine. But it sure sounds like fun.
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Brother exactly, that's what my Girlfriend said today, if you open it up, I know your going to "rebuild the whole engine" Hahaha she knows me ! She also said, just wait until "We" both have our new Trail masters (wow) and then you can build a hot engine for yours and your dirt drag bike, just fix this engine or get a new engine that you will be happy with using for hunting etc... ! Dang I'm a lucky man !!! Tks on the crank info, did not know if I was going to have to change bearings, side casing etc... Decisions, by the time I buy a crank, valves, push rods, rockers, flywheel. I will have spent enough to probably just buy a new engine, but will miss the fun of building it.
 
L

LIVIT

Well-Known Member
#9
#9
Strigoi said:
If you plan on swapping a billet rod into the engine you'll need to remove the crank anyway. Might as well just pick up a 3/4" crank and put it in that case when doing that.
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Yup, it's part of the decision on what too do here for sure. I do think that my intake valve is slightly damaged. So would need to replace all that too..
 
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panchothedog

Well-Known Member
#10
#10
MY MY. Isn't that the way it goes. The side cover is off so you certainly don't want to put a stock cam back in there. And that new cam is going to need some stronger springs, and that's going to make it rev higher so we just have to put in the billet rod. ect ,ect,ect. It's a lot of fun building these little engines, but if you don't have 2 or 3 extra $100 bills in your wallet it's better to just change the oil and maybe check the plug. ADDICTING.
 
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LIVIT

Well-Known Member
#11
#11
panchothedog said:
MY MY. Isn't that the way it goes. The side cover is off so you certainly don't want to put a stock cam back in there. And that new cam is going to need some stronger springs, and that's going to make it rev higher so we just have to put in the billet rod. ect ,ect,ect. It's a lot of fun building these little engines, but if you don't have 2 or 3 extra $100 bills in your wallet it's better to just change the oil and maybe check the plug. ADDICTING.
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Haha yup, I built and raced 8-9 second 1/4 drag cars for years. Also dirt bikes. With them it was $1,000 bills ! So for me this for sure is less expensive and I'm finding out a lot easier. It's the learning process in the difference with these little engines, that I'm having a lot of fun learning. I have a lot more projects coming up, dirt drag bike, a couple of Trail masters or something similar. Plus a full suspension yard cart. Yup, very addictive, but I love it and my Girl friend does too !!
 
DaddyJohn

DaddyJohn

Well-Known Member
#13
#13
I just wanted to chime in and say that I got a free 196cc engine off of a trash pump that had a threaded short crank stub. I took the cover off, swapped a $30 crank in there, didn’t touch anything else, and was well pleased with the results. :p
 
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LIVIT

Well-Known Member
#14
#14
DaddyJohn said:
I just wanted to chime in and say that I got a free 196cc engine off of a trash pump that had a threaded short crank stub. I took the cover off, swapped a $30 crank in there, didn’t touch anything else, and was well pleased with the results. :p
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Cool, free works for me. I actually replaced the 196 with a Wildcat 223 ( Love it ) I'm going to rebuild the 196 over the winter when my fishing guide biz slows down and hunting season is over. Where is a good source to get a 3/4 crank ?
 
SAS289

SAS289

Well-Known Member
#15
#15
L

LIVIT

Well-Known Member
#16
#16
L

LIVIT

Well-Known Member
#18
#18
DaddyJohn said:
I got my last one off of eBay for under $30.
https://www.ebay.com/itm/1545866943...lOrd06oQbO&var=&widget_ver=artemis&media=COPY
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Tks John, not sure exactly where I want to go with the 196 yet. I might build it for a young man with asbergers, who helps me out around property. He has a mini with an old B&S 3.5hp. Might be a good project for him to learn more about small engines ! I know for myself, it's Hemi Strokers like my Wildcat 223 for my bikes and big blocks for the karts.
 
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