[LittlebikesBigDreams]

added close to 2 inches on the expansion chamber… the header pipe was not shortened
only the chamber

still need to either upgrade to a 15mm carb or just port this one…..here’s a basic illustration from an old thread that should help any who also want to do this

 

[Atvrunner2]

It looks really good knowing how small these new pipes are. It is better than it was.
Either taper bore the round slide OR buy a 15mm pumper carb, which will need a new intake, velocity stack, gaskets and fuel lines as most pumper carbs utilize 2 lines.

 

[LittlebikesBigDreams]

It looks really good knowing how small these new pipes are. It is better than it was.
Either taper bore the round slide OR buy a 15mm pumper carb, which will need a new intake, velocity stack, gaskets and fuel lines as most pumper carbs utilize 2 lines.

the low end torque is actually pretty surprising, think i got a really good batch of a cag engine. i have this thing geared pretty long, 6/56. and it picks up with little to no problem, no slipping either (yet). considering the hda48d which is a 16mm.

 

[Atvrunner2]

Nice. Well, try that carb. I have never used one that big. The 15mm pumper on a modified engine, or 668 clones (some ported) and taper bored on slightly modded engines. Is your engine new? Probably a 40mm. But those have nice meat in the cylinder for heat dissipation. I do run both 40 and 44's.

 

[Atvrunner2]

I have a stock gutless 40 mm, I've been wanting to slowly modify it. I've always gone from gutless to extreme. I want to do just some simple boltons, see what the differences are and record them.

 

[LittlebikesBigDreams]

Nice. Well, try that carb. I have never used one that big. The 15mm pumper on a modified engine, or 668 clones (some ported) and taper bored on slightly modded engines. Is your engine new? Probably a 40mm. But those have nice meat in the cylinder for heat dissipation. I do run both 40 and 44's.

it’s new,only a couple gas tanks through it so far. 44mm head too.

 

[LittlebikesBigDreams]

I have a stock gutless 40 mm, I've been wanting to slowly modify it. I've always gone from gutless to extreme. I want to do just some simple boltons, see what the differences are and record them.

the plan is fbo then porting if i’m not satisfied with the result, a carb and exhaust alone wake them up a bit for sure,

 

[Atvrunner2]

the plan is fbo then porting if i’m not satisfied with the result, a carb and exhaust alone wake them up a bit for sure,

It sure does. Always the best first step. I have some older aftermarket pipes I will play with.

 

[kray15]

These new stock pipes are pathetic compared to the originals... And those weren't very good haha. The diffuser cone (expansion cone) should be way longer. On these new ones they just take two baffle cones and put them together. The original pipes had about 2-3 inches of header pipe after the final bend, instead of the 6-8inches they have now. The stock pipe mod would basically bring the expansion chamber straight up to the final bend as you can see in the drawing you posted. This also mimics the pipe off of the blata 2.5. While what you did will be helpful. I would be even tempted to cut even more off of the header pipe. However, because of the change of the expansion chamber design I really can't say if its the right thing to do and have you then ruin your pipe.

 

[Anastasi13]

what bike is that?

 

[LittlebikesBigDreams]

These new stock pipes are pathetic compared to the originals... And those weren't very good haha. The diffuser cone (expansion cone) should be way longer. On these new ones they just take two baffle cones and put them together. The original pipes had about 2-3 inches of header pipe after the final bend, instead of the 6-8inches they have now. The stock pipe mod would basically bring the expansion chamber straight up to the final bend as you can see in the drawing you posted. This also mimics the pipe off of the blata 2.5. While what you did will be helpful. I would be even tempted to cut even more off of the header pipe. However, because of the change of the expansion chamber design I really can't say if its the right thing to do and have you then ruin your pipe.

i thought so too on the header shortening, i actually own a 2.5 aswell and tried bolting that exhaust on but it doesn’t clear the head. probably going to go ahead and do that sometime soon. yeah these new pipes are horrible but we make it work.

 

[LittlebikesBigDreams]

what bike is that?

mototec 49cc 2 stroke which was really a 40cc 4 stroke. it’s been swapped with a cag engine, needed an entirely new mounting system but the frame is pretty cool. 40 mph is the goal with this build

 

[Atvrunner2]

That's a great goal. And about as comfortable I am going on one. Fastest I did years ago was 34mph.
@kray15 these new pipes are a joke. They do need about 6in in the belly and yes more header removed.
I have an older stock pipe, really close to the blata 2.5 pipe and way better then these newer ones. Even the header pipe is bigger in diameter.

 

[Atvrunner2]

i thought so too on the header shortening, i actually own a 2.5 aswell and tried bolting that exhaust on but it doesn’t clear the head. probably going to go ahead and do that sometime soon. yeah these new pipes are horrible but we make it work.
View attachment 162597

Find a good fabrication place near you and mimic the blata pipe but make it even better. I have a guy but was always too busy to make me a pipe.

 

[kray15]

oh nice, you've got a great frame of reference then. I would get some sheet metal and cut a proper lengthed diffuser cone. Use the dimensions from the blata. First test the bike with the pipe you have now. I'm curious how it performs still. Have you tried putting the blata motor in this frame? I have a cag with a blata 2.5 motor in it. Its crazy smooth.

 

[kray15]

That's a great goal. And about as comfortable I am going on one. Fastest I did years ago was 34mph.
@kray15 these new pipes are a joke. They do need about 6in in the belly and yes more header removed.
I have an older stock pipe, really close to the blata 2.5 pipe and way better then these newer ones. Even the header pipe is bigger in diameter.

I never thought the cag pipe would be something sought after haha. All those years of everyone trying to get rid of it and here we are wishing we had it.

 

[LittlebikesBigDreams]

oh nice, you've got a great frame of reference then. I would get some sheet metal and cut a proper lengthed diffuser cone. Use the dimensions from the blata. First test the bike with the pipe you have now. I'm curious how it performs still. Have you tried putting the blata motor in this frame? I have a cag with a blata 2.5 motor in it. Its crazy smooth.

swapping the 2.5 onto the frame isn’t something i foresee myself doing, the bike is all original with no rebuilds and i don’t plan on thrashing it around hard like this one. the pipe now performs alright but it can definitely be improved

 

[kray15]

swapping the 2.5 onto the frame isn’t something i foresee myself doing, the bike is all original with no rebuilds and i don’t plan on thrashing it around hard like this one. the pipe now performs alright but it can definitely be improved

I get that. I had bought my blata engine without the bike. and I had an open cag frame. It just worked out to perfectly.

 

[LittlebikesBigDreams]

I get that. I had bought my blata engine without the bike. and I had an open cag frame. It just worked out to perfectly.

parts for the 2.5 were super hard to come across when i looked before and it would’ve been a pain to replace something along the line, it gets love and is ridden but i intend to keep it a little more sheltered than this build. Kind of why its being built in the first place. post some pictures of that bike sounds sweet

 

[Atvrunner2]

I never thought the cag pipe would be something sought after haha. All those years of everyone trying to get rid of it and here we are wishing we had it.

I know, crazy. Every time I buy a used bike, I just look at the exhaust pipe and decide if I'm going to keep it and replace with the newer smaller one or or just resell. Ha.