Significant HP increase from chain drive conversion?

[trbig]

Many modern dual sport bikes have 14 tooth or smaller front sprockets. Most end up going down to at least a 13, while many use a 12 tooth. Many of these 650cc single cylinder bikes make more low-end torque than our Yamahas, while some have dual cylinders with as much displacement and more HP and it causes no excessive chain or sprocket wear to modern sprockets and chains. Many go until engine rebuild time with 50-60k miles on them with stock sprockets, though the chains do wear out usually sooner than that.. BUT.. those chains are routinely going through sand/mud etc.. Much harsher elements than simply riding down the road.

I can't vouch for what size sprockets go on crotch rockets, but trust what Steve says. That being said, with the 7 teeth versus 9 teeth a sprocket may grab at one time on these crotch rockets, you're also talking of most modern bikes making nearly double the HP our bikes make. I don't see you having a problem pushing a gear against a chain with 20% less surface area with only half the HP. With a modern o-ring chain with rollers, I doubt most of you would ever see a problem. And, as stated, there are many modern lubes out there for a chain (Not just wax based) that will not sling or fling off. For you people spending tons of money to make more HP with these bikes, this is going to be one of your cheapest options if you can talk XSChop into fabbing some more up for you. If you want smooth quiet reliability, leave it shaft driven.

[cywelchjr]

Many modern dual sport bikes have 14 tooth or smaller front sprockets. Most end up going down to at least a 13, while many use a 12 tooth. Many of these 650cc single cylinder bikes make more low-end torque than our Yamahas, while some have dual cylinders with as much displacement and more HP and it causes no excessive chain or sprocket wear to modern sprockets and chains. Many go until engine rebuild time with 50-60k miles on them with stock sprockets, though the chains do wear out usually sooner than that.. BUT.. those chains are routinely going through sand/mud etc.. Much harsher elements than simply riding down the road.

I can't vouch for what size sprockets go on crotch rockets, but trust what Steve says. That being said, with the 7 teeth versus 9 teeth a sprocket may grab at one time on these crotch rockets, you're also talking of most modern bikes making nearly double the HP our bikes make. I don't see you having a problem pushing a gear against a chain with 20% less surface area with only half the HP. With a modern o-ring chain with rollers, I doubt most of you would ever see a problem. And, as stated, there are many modern lubes out there for a chain (Not just wax based) that will not sling or fling off. For you people spending tons of money to make more HP with these bikes, this is going to be one of your cheapest options if you can talk XSChop into fabbing some more up for you. If you want smooth quiet reliability, leave it shaft driven.

I'll agree with you there, but most of those bikes also weight in at around half what these bikes weight, and that makes a HUGE difference in chain loading, especially at low speeds which IIRC from my HS shop classes is when wear on chains and such would be highest. Not saying it would be twice the wear though, but given the weight of the bike I wouldn't be feeling like I was getting the best wear from the chain that I could. Then again, even with modern chain drive, I still would rather deal with a shaft drive rather than a chain drive. I don't want to spend time cleaning a stupid chain on a street bike, I want to ride the thing. Now for a dual sport or dirt bike, that's a whole different story, but I wouldn't want to try and turn one of these into a dirt bike either .

[79XS11F]

I think anyone who is working on getting everything that they can out of the bike would not be too worried about chain life. The cost of a chain every now and then is nothing compared to the investment that will have been gone into creating the modified bike in the first place. The chain drive option also does a lot more then just put added HP to the ground. This mod removes a lot of sprung weight at the back end of the bike and if done as many will do, also allows for the use of wider modern profiled tires. I would guess that my modified bike is close to the weight of a 70s type 650 with what I have done to it but I did not go with an exotic swing arm setup so tire size is the usual that we see on these bikes. If that tire burns off too quickly, I will have to look at my options. Sprocket set up on my chain drive conversion is 13 / 39.
Rob

[cywelchjr]

I think anyone who is working on getting everything that they can out of the bike would not be too worried about chain life. The cost of a chain every now and then is nothing compared to the investment that will have been gone into creating the modified bike in the first place. The chain drive option also does a lot more then just put added HP to the ground. This mod removes a lot of sprung weight at the back end of the bike and if done as many will do, also allows for the use of wider modern profiled tires. I would guess that my modified bike is close to the weight of a 70s type 650 with what I have done to it but I did not go with an exotic swing arm setup so tire size is the usual that we see on these bikes. If that tire burns off too quickly, I will have to look at my options. Sprocket set up on my chain drive conversion is 13 / 39.
Rob

While I agree with your conclusions you have your terminology backwards. Weight removed from the portion of the bike NOT supported by the springs is UNSPRUNG weight rather than sprung weight which is indeed a good thing from a handling matter.

[79XS11F]

While I agree with your conclusions you have your terminology backwards. Weight removed from the portion of the bike NOT supported by the springs is UNSPRUNG weight rather than sprung weight which is indeed a good thing from a handling matter.

My Bad ... but both are reduced with the chain drive mod.
Rob

[cywelchjr]

My Bad ... but both are reduced with the chain drive mod.
Rob

I think if you do the math , the majority decrease is unsprung weight though, as it's in the parts that are not supported by the suspension, thus making for better handling and better suspension action.

[joceiphus]

I think anyone who is working on getting everything that they can out of the bike would not be too worried about chain life. The cost of a chain every now and then is nothing compared to the investment that will have been gone into creating the modified bike in the first place. The chain drive option also does a lot more then just put added HP to the ground. This mod removes a lot of sprung weight at the back end of the bike and if done as many will do, also allows for the use of wider modern profiled tires. I would guess that my modified bike is close to the weight of a 70s type 650 with what I have done to it but I did not go with an exotic swing arm setup so tire size is the usual that we see on these bikes. If that tire burns off too quickly, I will have to look at my options. Sprocket set up on my chain drive conversion is 13 / 39.
Rob

A chain drive would also let you use lighter wheels.