Hey guys, my name's Brandon and I've been researching a big bore stroker motor for a kx125. My bike is a 2003 but I have access to a 2005 kx125 motor for a relatively small price that I would use for the build to keep my stock motor for re-sale in the future.
I've researched all the costs I believe are involved in this and just have some questions about a build like this. I've done some researce and found some stroking topics, including Eric's crankshaft smoking post(very informative) but still have some questions I'd like to ask. First, I have a price list of all the parts/services I believe I will require. Please let me know of anything I may have left out.
$475 for bore, port, piston, gasket, head mod, and re-plate Eric Gorr 144 kit
$46 shipping for cylinder(round trip) USPS
$495 for crank stroking, truing, and balancing from crankworks
$105 for new connecting rod kit from hotrods
$50 shipping for crank(round trip) USPS
$45 cylinder spacer from Cometic
$60 gaskets & misc bearings from Cometic & others
$???.00 Crankcase boring by Eric
$1286.00 for whole 2005 kx154 stroker engine
+ Crankcase boring and customs/brokerage at the border(if either is needed) and the 2005 bottom and top end.
My first question is if I were to have the 144 kit done by Eric could I have my crank stroked at a later date with out problems? Or would having the bike stroked change how Eric would perform the work on my cylinder and be something I'd need to inform him of?
Second question is about the crank stroking. I noticed the work to have the crank stroked is roughly double the cost of a new Hot Rods crank. I also know Hot Rods is offering complete cranks already stroked for not a whole lot more than the cost of one of thier stock replacements. Does anyone on here have any inside information pertaining to whether Hot Rods will be offering such a crank for my bike in the near future?
Also, I've heard talk of another company aside from crankworks called TNR. Do they have a website? E-mail? And can anyone tell me how their pricing and quality of work compares to crankworks?
What about rod length? I don't know how exactly how it effects anything(other than clearance of the crank and head).
Next are a list of things eric identified as being effected when you modify the stroke of an engine:
1) The displacement is increased.
2) The port timing is advanced.
3) The ignition timing is advanced.
4) The compression ratio of the combustion chamber and crankcase are increased.
5) The reed valve timing is advanced and the reed lift is increased.
6) The piston speed is greater at any given rpm.
7) The maximum piston speed is reached at a lower rpm.
8) The rod bearing wear is accelerated.
9) The rod ratio is decreased.
10) The bore to stroke ratio is altered.
The only ones that I don't believe I have solved are 5) and 9). All the others I think are either desired(increase in displacement) or remedied by a spacer(compression and timing) I want to know what effects an increase in reed lift and decreasing the rod ration will have on the motor.
The piston speed was mentioned in the smoking post and specified as 4500ft/min I calculated the average for a 58mm stroke at 11000rpm and its about 1.3km/min or somewhere around 4000ft/min so I think I'm fine there. I mainly would like to know more about side effects 5 and 9.
Now for the next thing. The connecting rod big end to crank case clearance. Can this be done at home with a dremmel and grinding wheel? I read in another post about crankcase turbulance so there's no real aerodynamic qualities I need worry about correct? Just grind down to where the crank will fit(if required) The 58mm stroke would require the pin to be relocated 1.75mm farther out from center, is this likely to be enough to require crankcase boring? Is there a minimum big end to case clearance? And finally if this cannot be done by myself(and is required) would eric do it and for what charge?
Almost done, what about carb jetting? I have a 410 installed now but with a larger engine I assume you'd have to go bigger on jetting a bit(maybe even carb boring?). What should I expect?
Now, my final problems aren't real big, just using the spacer will move my reeds, pipe and head mount bracket all up 1.75mm(other than the head mount these should still fit together alright though, being rubber mounted).
WOW theres alot more to this than I thought when I first got the idea to have my engine stroked.....
Well, I think that's everything I wanted to know about. Thanks in advance for any help and if I do go through with this I'll get pictures of the work, assembly, and write a review comparing my stock 2003 to the modified 2005 engine. And if I can locate somewhere local for a reasonable price, I'll get a dyno. Biggest obstacle now is raising up enough money before spring to get the work done.
I've researched all the costs I believe are involved in this and just have some questions about a build like this. I've done some researce and found some stroking topics, including Eric's crankshaft smoking post(very informative) but still have some questions I'd like to ask. First, I have a price list of all the parts/services I believe I will require. Please let me know of anything I may have left out.
$475 for bore, port, piston, gasket, head mod, and re-plate Eric Gorr 144 kit
$46 shipping for cylinder(round trip) USPS
$495 for crank stroking, truing, and balancing from crankworks
$105 for new connecting rod kit from hotrods
$50 shipping for crank(round trip) USPS
$45 cylinder spacer from Cometic
$60 gaskets & misc bearings from Cometic & others
$???.00 Crankcase boring by Eric
$1286.00 for whole 2005 kx154 stroker engine
+ Crankcase boring and customs/brokerage at the border(if either is needed) and the 2005 bottom and top end.
My first question is if I were to have the 144 kit done by Eric could I have my crank stroked at a later date with out problems? Or would having the bike stroked change how Eric would perform the work on my cylinder and be something I'd need to inform him of?
Second question is about the crank stroking. I noticed the work to have the crank stroked is roughly double the cost of a new Hot Rods crank. I also know Hot Rods is offering complete cranks already stroked for not a whole lot more than the cost of one of thier stock replacements. Does anyone on here have any inside information pertaining to whether Hot Rods will be offering such a crank for my bike in the near future?
Also, I've heard talk of another company aside from crankworks called TNR. Do they have a website? E-mail? And can anyone tell me how their pricing and quality of work compares to crankworks?
What about rod length? I don't know how exactly how it effects anything(other than clearance of the crank and head).
Next are a list of things eric identified as being effected when you modify the stroke of an engine:
1) The displacement is increased.
2) The port timing is advanced.
3) The ignition timing is advanced.
4) The compression ratio of the combustion chamber and crankcase are increased.
5) The reed valve timing is advanced and the reed lift is increased.
6) The piston speed is greater at any given rpm.
7) The maximum piston speed is reached at a lower rpm.
8) The rod bearing wear is accelerated.
9) The rod ratio is decreased.
10) The bore to stroke ratio is altered.
The only ones that I don't believe I have solved are 5) and 9). All the others I think are either desired(increase in displacement) or remedied by a spacer(compression and timing) I want to know what effects an increase in reed lift and decreasing the rod ration will have on the motor.
The piston speed was mentioned in the smoking post and specified as 4500ft/min I calculated the average for a 58mm stroke at 11000rpm and its about 1.3km/min or somewhere around 4000ft/min so I think I'm fine there. I mainly would like to know more about side effects 5 and 9.
Now for the next thing. The connecting rod big end to crank case clearance. Can this be done at home with a dremmel and grinding wheel? I read in another post about crankcase turbulance so there's no real aerodynamic qualities I need worry about correct? Just grind down to where the crank will fit(if required) The 58mm stroke would require the pin to be relocated 1.75mm farther out from center, is this likely to be enough to require crankcase boring? Is there a minimum big end to case clearance? And finally if this cannot be done by myself(and is required) would eric do it and for what charge?
Almost done, what about carb jetting? I have a 410 installed now but with a larger engine I assume you'd have to go bigger on jetting a bit(maybe even carb boring?). What should I expect?
Now, my final problems aren't real big, just using the spacer will move my reeds, pipe and head mount bracket all up 1.75mm(other than the head mount these should still fit together alright though, being rubber mounted).
WOW theres alot more to this than I thought when I first got the idea to have my engine stroked.....
Well, I think that's everything I wanted to know about. Thanks in advance for any help and if I do go through with this I'll get pictures of the work, assembly, and write a review comparing my stock 2003 to the modified 2005 engine. And if I can locate somewhere local for a reasonable price, I'll get a dyno. Biggest obstacle now is raising up enough money before spring to get the work done.
