No matter what I do top speed stays constant.

[Jayraye39]

So my bike tops out at 43-45 mph then hits a wall. Ive changed pipe designs from header to stinger. boring out my carb and generally eveything else in between. i have ported my cylinder as far wide as it can go. that was my main goal was port with. while porting i didnt measure how much I may have took off the top of the exhaust window. so I never ported it at the roof. I know in order to get more rpm and top speed i need to raise the exhaust roof. I have a G4 cylinder from top of jug to top of ex port is 27mm from top of ex port to bottom of ex port is 15mm tall and im 27.5 wide. Does it sound like I have room to take off the top some more. im not sure what a good port hight is. Also I never lowered the intake port because I shaved my piston skirt. Can I still lower my intake port eventhough i trimmed my piston skirt.

 

[Jayraye39]

My intake port is 43mm from top of jug by 12mm top and bottom of port by 22mm wide. can improvement be made here aswell

 

[Sidewinder Jerry]

My intake port is 43mm from top of jug by 12mm top and bottom of port by 22mm wide. can improvement be made here aswell

Are you able to ride in a position to get the least amount of wind resistance? How much have you invested into your wheels? Is there any weight you can get rid of without compromising safety?

Some times you've done all that can be done with a particular engine. So unless you change to a higher performance engine, you have to start considering other factors which can add speed.

 

[Wrench]

The improvement your looking for is called AM6

 

[Sidewinder Jerry]

I do like your question though.

How far can you take porting/trimming/mods to get max performance before it's too much?

 

[GW's Motorized]

Are you perhaps running out of gear?

 

[Jayraye39]

I think that yes im probly on the brink of a maxed out motor and clutch. So my only alternative for gaining higher speeds would be like GW said my gearing. Since their is absolutly no effect of performance by changing sertain performace parts out does lead me to believe that is could be exactly that im just out of gear maxed.

So the alternative goes back to what I was advized earlier this year. go down to a 32 tooth wheel sprocket or and 11 tooth drive sprocket.. So thats what ill do. I dont want the bike to be stupid to drive cause of the high gearing. I think i heard the 11t drive sprocket would be like having a 33 tooth rear sprocket. so its a hair bigger than a 32 which stops and starts will be alittle better. but I also heard the drive sprocket change would be better for the motor strain. But yeah I think yall are right the speed cuttoff on my bike is to consistant. so no more motor mods. only left with power transfer mods

 

[Sidewinder Jerry]

I think that yes im probly on the brink of a maxed out motor and clutch. So my only alternative for gaining higher speeds would be like GW said my gearing. Since their is absolutly no effect of performance by changing sertain performace parts out does lead me to believe that is could be exactly that im just out of gear maxed.

So the alternative goes back to what I was advized earlier this year. go down to a 32 tooth wheel sprocket or and 11 tooth drive sprocket.. So thats what ill do. I dont want the bike to be stupid to drive cause of the high gearing. I think i heard the 11t drive sprocket would be like having a 33 tooth rear sprocket. so its a hair bigger than a 32 which stops and starts will be alittle better. but I also heard the drive sprocket change would be better for the motor strain. But yeah I think yall are right the speed cuttoff on my bike is to consistant. so no more motor mods. only left with power transfer mods

To do 45 mph on 26" wheels using a 10/36 means your engine is doing 8587 rpm. If you do go to the 11t drive but still have the same speed at full throttle, then it means your engine has reached its load limit. If with the 11t you're still doing 45 mph at full throttle then your engine has dropped to 7806 rpm due to the increased load.

By using the 11t, if it can handle the additional load without dropping the rpm you should see a speed increase to 49.5 mph

 

[Jayraye39]

To do 45 mph on 26" wheels using a 10/36 means your engine is doing 8587 rpm. If you do go to the 11t drive but still have the same speed at full throttle, then it means your engine has reached its load limit. If with the 11t you're still doing 45 mph at full throttle then your engine has dropped to 7806 rpm due to the increased load.

By using the 11t, if it can handle the additional load without dropping the rpm you should see a speed increase to 49.5 mph

nice breaking 50 is what ive been tryna do for the past year. if an 11t could get me their I would be ecstatic. then i could move on to a new build and bigger motor

 

[cloakedvillain]

Dropping down to a 30 tooth rear could do it too. Assuming the engine has any more to give.