Ohh, so what exactly do they do? And nope, mine is in good condition. I just need to start it and see..and the previous previous owner said he had it as a spare dor either sprint track racing, or something... I hope it doesnt grind or make any noise. Im now looking up motor mounts for the engine.
ferio 1st and custom shifter kart build!!
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the motor uses 2 radiators. i can mount one on the motor side, would i be able to put the second radiator on the left side?im aware the hoses will be extremely long..lol. will it be efficient having such a long hose? or what i be able to get away with one radiator?
maxpower49
Member
One thing I highly recommend with two stroke engines is a leak down test after you finish the rebuild, I am not talking about a normal leak down test like the ones done on a four stroke but one that will pressure test the entire engine down to the crank seals and all gaskets that are pressurized during normal operation.
I will get you a picture of my homemade tester that is pretty easy to build, on a two stroke when you have a leaking seal or gasket you are loosing your oil, fuel, air mixture and running the engine lean and can cause all sorts of running issues or even melt down the engine.
One more thing, you might get lucky but normally to get to the crankshaft and get it open all the way to the transmission you need a special tool called a case spliter, sometimes they are nice to you and they just kinda tap apart with a rubber mallet but it depends on how the engine wants to act that day.
---------- Post added at 05:26 PM ---------- Previous post was at 04:43 PM ----------
This is a homemade two stroke leak down tester, basically you find a pvc T fitting that will fit snugly in the carb boot (the rubber thing you removed before the reed cage) and you cap two of the ends and in one end you install a pressure gauge and the other a schrader valve to fill with compressed air from a bike pump (make sure you use a bike or hand pump an air compressor will fill the engine way too fast), you will also need a rubber cap that fits over the exhaust outlet.
You want a low pressure gauge because you only pump the engine up to 6psi, any more you will blow out a crank seal or cause some other issues. To use it you clamp the tester into the carb boot in place of the carb, you close off the exhaust and make sure the spark plug is installed as well you want the engine air tight. Then you take a bike pump, and pressurize the engine up to the mentioned 6psi and watch the tester.
The general rule of thumb I go by is you do not want to lose more that 1psi of air per minute over six minuets, a slight leak is decent (as long as it is less then 1psi per minute) but I usually shoot for completely air tight because the fewer leaks the better.
If you hold the pressure then engine is good to go if you do leak badly then you bust out some soapy water in a spray bottle and just keep spraying anywhere there is a gasket or seal and look for air bubbles, then seal and repeat. Also spray the schrader valve where you fill it and make sure that isn't leaking, I chased my tail for a day or so looking for a leak before I realized there was a slight leak in the bike pump I was using...
Sorry about the wall of text but I enjoy messing with two strokes and have messed with a few over time :arf:
I will get you a picture of my homemade tester that is pretty easy to build, on a two stroke when you have a leaking seal or gasket you are loosing your oil, fuel, air mixture and running the engine lean and can cause all sorts of running issues or even melt down the engine.
One more thing, you might get lucky but normally to get to the crankshaft and get it open all the way to the transmission you need a special tool called a case spliter, sometimes they are nice to you and they just kinda tap apart with a rubber mallet but it depends on how the engine wants to act that day.
---------- Post added at 05:26 PM ---------- Previous post was at 04:43 PM ----------
This is a homemade two stroke leak down tester, basically you find a pvc T fitting that will fit snugly in the carb boot (the rubber thing you removed before the reed cage) and you cap two of the ends and in one end you install a pressure gauge and the other a schrader valve to fill with compressed air from a bike pump (make sure you use a bike or hand pump an air compressor will fill the engine way too fast), you will also need a rubber cap that fits over the exhaust outlet.
You want a low pressure gauge because you only pump the engine up to 6psi, any more you will blow out a crank seal or cause some other issues. To use it you clamp the tester into the carb boot in place of the carb, you close off the exhaust and make sure the spark plug is installed as well you want the engine air tight. Then you take a bike pump, and pressurize the engine up to the mentioned 6psi and watch the tester.
The general rule of thumb I go by is you do not want to lose more that 1psi of air per minute over six minuets, a slight leak is decent (as long as it is less then 1psi per minute) but I usually shoot for completely air tight because the fewer leaks the better.
If you hold the pressure then engine is good to go if you do leak badly then you bust out some soapy water in a spray bottle and just keep spraying anywhere there is a gasket or seal and look for air bubbles, then seal and repeat. Also spray the schrader valve where you fill it and make sure that isn't leaking, I chased my tail for a day or so looking for a leak before I realized there was a slight leak in the bike pump I was using...
Sorry about the wall of text but I enjoy messing with two strokes and have messed with a few over time :arf:
No this is perfect! My mom has some pvc elbows and random stuff to make. Im going to try this on the engine now. If its good, i wont have to get new gaskets even though i want to! Any more tips and tricks to look out for? Its my first 2 stroke engine im dealing with.
maxpower49
Member
They are fairly simple little things, the biggest killer of two strokes (other than old age) is leaks, make sure there is no air leaks in the engine or anywhere in the exhaust as well, exhaust leaks can also cause lean conditions running into the same issues mentioned above. The exhaust is actually pretty important on tuned two strokes that can impact power gains, loss, more torque more, top end rpm it can really change the feel of the engine, so don't go adding a straight pipe to the thing haha.
The second biggest issue is jetting, make sure you jet the carb properly. Whenever you run a two stroke lean from improper jetting you are not only running it hot from too little fuel but that fuel also contains the oil it needs so it is a double threat, hot engine low oil = melted piston, broken stuff.
Finally compression, depending on what is done you want to make sure you run the proper octane fuel in your engine, if it is stock 87/89 should be good however if someone bumped the compression for more power you might be in the 91/93 octane range (or higher depending if the person wanted to run race gas), if you run lower octane fuel than what you need it causes detonation that causes broken piston rings, chewed cylinders excessive wear on bearings. This seems to be more of a issues with two strokes than four because more people seem to bump up the compression because it is fairly easier on two strokes.
The second biggest issue is jetting, make sure you jet the carb properly. Whenever you run a two stroke lean from improper jetting you are not only running it hot from too little fuel but that fuel also contains the oil it needs so it is a double threat, hot engine low oil = melted piston, broken stuff.
Finally compression, depending on what is done you want to make sure you run the proper octane fuel in your engine, if it is stock 87/89 should be good however if someone bumped the compression for more power you might be in the 91/93 octane range (or higher depending if the person wanted to run race gas), if you run lower octane fuel than what you need it causes detonation that causes broken piston rings, chewed cylinders excessive wear on bearings. This seems to be more of a issues with two strokes than four because more people seem to bump up the compression because it is fairly easier on two strokes.
Ahh! Good stuff. I wasnt sure what about the whole jetting or the leaks. I mean i know leaking isnt good but the whole exhaust thing is a bid deal. Im not sure what exhaust im going to put on it. Should i use a aftermarket dirtbike exhaust?im not exactly worried about the motor as of right now because im not at that stage just yet. If my bro comes through tomorrow with the super wide wheels, and my packages come in couple days! Ill be seeking your advice once there!. So what do you think about my radiator situation? Run 1 radiator on each side? Or 2 dual row radiator? I would kind of like the look of a radiator on each side! Sweeet lol
maxpower49
Member
Exhaust is mostly personal preference or whatever you can get to fit haha, but the best thing I can recommend is to search around online and see what people have to say about how different pipes preform then go what what you would like to run or at least fits your budget.
Radiators is also person preference as long as it meets or exceeds what came on the original dirt bike, also make sure that the fill point or points are mounted higher than the top of the engine, makes bleeding the air out much simpler. If you decide to go single radiator I recommend a banshee aftermarket radiator, they are reasonably priced and are capable of cooling down a 350cc two cylinder two stroke engine, so food for though.
I'll be watching this build so I'll be tuned in, you just happened to strike the cord that I know a decent amount about so any engine help I'll be glad to help! There are others much more knowledgeable about the kart itself
Radiators is also person preference as long as it meets or exceeds what came on the original dirt bike, also make sure that the fill point or points are mounted higher than the top of the engine, makes bleeding the air out much simpler. If you decide to go single radiator I recommend a banshee aftermarket radiator, they are reasonably priced and are capable of cooling down a 350cc two cylinder two stroke engine, so food for though.
I'll be watching this build so I'll be tuned in, you just happened to strike the cord that I know a decent amount about so any engine help I'll be glad to help! There are others much more knowledgeable about the kart itself
As far as the exhaust goes:
Most of the images i see of go kart exhausts are the skinny bicycle immer tube sized exhaust that comes out the back and goes behind the seat lol. Is that a custom pipe or the common design?ive been thinking about getting a dirtbike exhaust(super skinny beginning, then crazy fat middle, then super skinny again) design and i was wondering.. do those come with a muffler? Or not? Are the muffler part needed for performance?
As far as radiators go:
I dont have any clue as to how the cooling system works haha. I dont know what line goes to where on the engine, and id like to get just a single radiator, but i think dual radiator will just be badass!!lol. I know fabrication will be needed for the mounts, which is fine. I just didnt know if the tubes are too long, you lose efficiency. Which i dont want!.
So i messed with the carb last night, just to see how it works. I now know the orientaton of it hahah! Didnt even know the way it was supposed to go, and look at me talk about building a custom kart LOL!. Is there anyway to tell what the jet sizes are before just buying sets? Or should i worry about thatt as i get to the motor stage?
So as far as an update goes. I order an oem igniton coil from ebay since the one i got wasnt the right one. 30 bucks so thats no big deal. I need splines done for my custom ahift linkage set up, so i emailed some shops who do spline cutting, so hopefully they get to me soon! I hope my bro comes with those wheels!
---------- Post added at 04:17 PM ---------- Previous post was at 04:10 PM ----------
Those ****ers arent here soo.. lol
Most of the images i see of go kart exhausts are the skinny bicycle immer tube sized exhaust that comes out the back and goes behind the seat lol. Is that a custom pipe or the common design?ive been thinking about getting a dirtbike exhaust(super skinny beginning, then crazy fat middle, then super skinny again) design and i was wondering.. do those come with a muffler? Or not? Are the muffler part needed for performance?
As far as radiators go:
I dont have any clue as to how the cooling system works haha. I dont know what line goes to where on the engine, and id like to get just a single radiator, but i think dual radiator will just be badass!!lol. I know fabrication will be needed for the mounts, which is fine. I just didnt know if the tubes are too long, you lose efficiency. Which i dont want!.
So i messed with the carb last night, just to see how it works. I now know the orientaton of it hahah! Didnt even know the way it was supposed to go, and look at me talk about building a custom kart LOL!. Is there anyway to tell what the jet sizes are before just buying sets? Or should i worry about thatt as i get to the motor stage?
So as far as an update goes. I order an oem igniton coil from ebay since the one i got wasnt the right one. 30 bucks so thats no big deal. I need splines done for my custom ahift linkage set up, so i emailed some shops who do spline cutting, so hopefully they get to me soon! I hope my bro comes with those wheels!
---------- Post added at 04:17 PM ---------- Previous post was at 04:10 PM ----------
There are others much more knowledgeable about the kart itself
Those ****ers arent here soo..
lol
maxpower49
Member
Four strokes are a little less picky about their exhaust, and straight pipes are often added for more noise and flow. Two strokes have an expansion chamber, the fat looking cone shaped deal, on two strokes some of the fuel and air actually escape out of the exhaust and the expansion chamber funnels it back into the cylinder with all sorts of fancy math to the correct ammount of back pressure. The slinecer part at the end is all part of the back pressure so a properly packed and the correct one to go with the pipe you buy is important, however most exhaust systems include the entire assembly.
The carb will have two jets that you should be able to remove and they have the size stamped on them, one will be really small and that is the piolit jet that controls idle to a slight extent, the larger one is the main jet and is the main one to mess with depending on size and mods.
On the shift linkage I would just modify a cheap oem shift shaft with a little cutting and welding (if you have the tools) but it will already be the correct spline.
And they will show up they just want more pictures haha.
The carb will have two jets that you should be able to remove and they have the size stamped on them, one will be really small and that is the piolit jet that controls idle to a slight extent, the larger one is the main jet and is the main one to mess with depending on size and mods.
On the shift linkage I would just modify a cheap oem shift shaft with a little cutting and welding (if you have the tools) but it will already be the correct spline.
And they will show up they just want more pictures haha.
Ah, i always wondered about the big fat part lol. Do i need to buy an exhaust for the cr125? Does it matter what year i get the exhaust for? Hows it going to look when i have the siliencer hanging 3 feet past the kart?lol maybe weld an elbow so it goes to the back of the seat? Im going to need help with the seat mounting because my kart doesnt have any tabs. I dont have tools for cutting an welding, but ill take it to the shop and see whats what. I still need to worry about the engine mount!. **** i might have a little side problem. A small piece of the metal that leads to the coolant line was rotted off, so im going to have to jb weld it. And i need to find the gasket for that. Ill be uploading more pics soon enough, but keep the info coming!
It needs to be for the year of your bike. Multiple years will work more than likely. But the bends have to line up and the flanges.
And a dirtbike style isn't that bad. Here is a kx125 shifter I redid last summer. It had a aftermarket pipe and silencer...........
And a dirtbike style isn't that bad. Here is a kx125 shifter I redid last summer. It had a aftermarket pipe and silencer...........
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Its not that bad yeah, but i want mine to curl behind the seat. Not really to fond of it just sticking out the back like that.. but im always open to ideas, so i will keep your idea as well.. wouldnt all cr125 share the same flange? Some questions for you joe.
whats holding up your muffler?
how did mount your motor on the frame?
How did you convert your throttle cable to the rod for the pedal?
Are your lines ran under the seat?
Do you have a skid plate for the seat as well?
Whats your opinion about my possible radiator set up?
How far back does the motor sit behind the seat?
---------- Post added at 07:39 AM ---------- Previous post was at 07:37 AM ----------
How fast did your kart go?
whats holding up your muffler?
how did mount your motor on the frame?
How did you convert your throttle cable to the rod for the pedal?
Are your lines ran under the seat?
Do you have a skid plate for the seat as well?
Whats your opinion about my possible radiator set up?
How far back does the motor sit behind the seat?
---------- Post added at 07:39 AM ---------- Previous post was at 07:37 AM ----------
How fast did your kart go?
maxpower49
Member
Most bikes have a similar flange but part of the fancy math that make expansion chambers work involve the bore and stroke of the engine, different years can have different bore/stroke combos to add up to about the same engine displacement. However if the engine did not change much or at all then you can use any exhaust system you want as long as it fits a cr125, but that would require a little more research specific to the cr's.
If you modify an expansion chamber to curl the way you way you want to you have to make sure you do not add or remove any pipe, you can curl them how you want but it is important to make sure they have the same displacement when you finish so no adding or removing any metal.
If you modify an expansion chamber to curl the way you way you want to you have to make sure you do not add or remove any pipe, you can curl them how you want but it is important to make sure they have the same displacement when you finish so no adding or removing any metal.
Ok here we go i hope..............
1. Only thing holding that muffler was that piece of strap with a tab welded on the end of the pipe.
2. I had a true QRC karts shifter engine mount for it.
3. Throttle cable was stock dirtbike throttle cable with a shifter kart linkage and rod on it.
4. Lines were wherever they could go without getting burnt ! (you will figure out why i said this when you get to that point. lol)
5. No skid plate. Always driven on streets so no issues.
6. If you notice mine is the factory 2 piece radiator bolted together with 2 bolts and nuts.
7. Motor was pretty much right next to the seat back and about 3/4" away from the seat cause the coolant line would not fit between them.
8. If geared correctly this kart would do 100+in 6th
Also my rebuild thread is on this forum. It was title QRC outlaw shifter kart and its under go kart discussion a few pages back. Shows the teardown and rebuild.
Poboy kartman
Senior Moments Member
Well.....let's put this in perspective real quick.....ummmmm....it's not reed valves that give two strokes "power".....
Four strokes have valves and some two strokes have reed plates that perform the same function....
Two strokes get their "power" from high rpm's......
No no, i didnt want to modify the expansion chamber, i just wanted to add a bend when it gets really skinny. Like the last inch or 2 of the exhaust, then when it curves behind the seat, then ill add the muffler to it.
---------- Post added at 02:19 AM ---------- Previous post was at 02:17 AM ----------
what is the name of a throttle cable for dirtbikes? I notice the end that goes into the carb has like a small numb at the end. Whats the term so i know which to get? Can i delete the rod and run just a cable? Provided if i get one long enough?
---------- Post added at 02:24 AM ---------- Previous post was at 02:19 AM ----------
I want to thank you guys for giving me so much knowledge! Appreciate it to the fullest!!! And expect some pics in the next week or so. Bought a ****load of parts and i plan on buying more. Whe im waiting for the parts to come, im going to try getting the motor to start. Any info on how to use jb weld?
Ferio....please DO NOT use bad language on the forum. This is a family orientated forum and we would like to keep it that way
DirtyDamage
New member
Curious, what's the jb weld going to be used for. It's easy just follow the directions on the box....personally j like to wear gloves...
crazykart
Crazy member
I like to get the slower setting jb weld, get a big syringe, mix the jb weld in a small bowl or cup, then put it in the syringe and use that to apply it. Have to work quick though.
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