Tinkering with stock exhaust

Vikingimike01

Active Member
Joined
Jul 1, 2018
Messages
768
Hey forum!

I have a 66cc 2 stroke, slightly ported at skirt, widened intake port, and also sanded a very little bit for compression. (The porting I did is very minimal!)

I've had a banana pipe, and had 60km/h top speed with that, but it was hard to fit, had to use 2 gaksets, had leaks with it... And I didn't like the whining noise it had.

I'm looking to modify the stock exhaust in some way or form, to achieve a bit higher top speed. Currently, i have the end cap baffle part off (The part held on by 1 nut) and I love the deep grunt it has at idle. It starts bogging at about 40km/h, and bogs untill like 42, then doesn't bog untill 44, then it bogs untill 46 and so on. I've had the same problem with my banana pipe, but it bogged from 40-45km/h straight, and once it got over that speed it didn't.

First, how do I fix the bogging? Too lean? The C Clip is at the lowest position alredy, it has 4 positions. It still accelerates but slower, Then when it stops bogging it accelerates normally.

Second. I want to do something with the stock exhaust, to keep that "loud" grunt, not muffle it too much, but still have higher speeds. I alredy cut off the pipe from the baffle part, to the edge of the actual baffle. I'm not sure what tool I can use to reach in there, to cut off the remaining pipe.

I know inside the exhaust part, there are plates. Should I cut them out as well? It has the one where the baffle's pipe part goes into to align it, but since it's areldy cut off, could I take out that plate part?
 


junglepig

Active Member
Joined
Oct 30, 2018
Messages
218
I don't know any tricks that will do anything for you with the stock exhaust, except make it louder. If I understand the state of your stock exhaust, you may need to chuck it in a vise, and then get maybe a needle-nose vice-grip pliers on the remaining internal tube and pull it out. It may take some elbow-grease. A tuned expansion chamber exhaust is really where you can get a big performance gain though.

But once you've settled on an exhaust system, you'll need to adjust your main jet for best performance at WOT, and after that, work with the needle position for your mid-range mixture. Just remember, any changes you make to the exhaust may require you to rejet the carb.

Which carb are you running?

Full disclosure - I have limited experience myself with the HT engine. I have mostly "book-knowledge" at present and more experienced members will be able to help more, and make us both more knowledgeable.
 

Vikingimike01

Active Member
Joined
Jul 1, 2018
Messages
768
I have the stock NT carb, with 65 jets. I feel like it's just not enough in the winter here in 5-10 celsius. The idle is high, goes down slowly. Maybe problems with the clutch adjustment again (The clutch lever was left pulled in for 2-3 weeks, maybe it got looser.)

I put the baffle part back in, didn't see any performance gains or loses... But I don't like the weird poof poof noise it makes now, i liked the old grunt better.

I can't get a tuned expansion pipe right now. I could only buy one from Europe, since the shipping from america is usually the same price of the product...

I do have a banana pipe, wich has better top speed. Could I modify that in any way, to make it have a deeper grunt? For example cut off the old muffler without the end cap baffle part, and somehow weld it on?
 

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
3,718
I have the stock NT carb, with 65 jets. I feel like it's just not enough in the winter here in 5-10 celsius. The idle is high, goes down slowly. Maybe problems with the clutch adjustment again (The clutch lever was left pulled in for 2-3 weeks, maybe it got looser.)

I put the baffle part back in, didn't see any performance gains or loses... But I don't like the weird poof poof noise it makes now, i liked the old grunt better.

I can't get a tuned expansion pipe right now. I could only buy one from Europe, since the shipping from america is usually the same price of the product...

I do have a banana pipe, wich has better top speed. Could I modify that in any way, to make it have a deeper grunt? For example cut off the old muffler without the end cap baffle part, and somehow weld it on?
What your describing Sounds like you need to Jet up a size or 2. High idle and long wind down is a lean condition. You'll need a summer and a winter jet.
 

Vikingimike01

Active Member
Joined
Jul 1, 2018
Messages
768
I have a 65 jet right now and the old 70. I'll reinstall the 70 jet since it's winter. I alredy know that I have to change jets, that's why I got a leaner one (Was running rich in the summer)

What can I do with my exhaust tho? The banana one. I'd love it if it wasn't for that whiny noise. And if I take the baffle off the stock one, it just spews oil on my shoes.
 

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
3,718
I have a 65 jet right now and the old 70. I'll reinstall the 70 jet since it's winter. I alredy know that I have to change jets, that's why I got a leaner one (Was running rich in the summer)

What can I do with my exhaust tho? The banana one. I'd love it if it wasn't for that whiny noise. And if I take the baffle off the stock one, it just spews oil on my shoes.
I would just keep checking to see when mzmiami gets some more mz65 pipes back in stock and get one of them. They work pretty well. 1hp bolt on is hard to beat without modding a kx or yz85 pipe to fit.
 

Vikingimike01

Active Member
Joined
Jul 1, 2018
Messages
768
Yeah. But still, I can't order anything from america. For example, a 60 USD product costs 70 USD to ship here.

I could maybe buy a used 2 stroke, 80cc pipe from somewhere, see if it fits, and try and cut off the part that goes on the exhaust port, and weld it on?
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
3,103
Yeah. But still, I can't order anything from america. For example, a 60 USD product costs 70 USD to ship here.

I could maybe buy a used 2 stroke, 80cc pipe from somewhere, see if it fits, and try and cut off the part that goes on the exhaust port, and weld it on?
There are lots of good two stroke 50-70cc pipes used on scooters that you would have access to,and if you can weld and fit it or get someone to do it you'll be quite pleased I'm sure.Europe has alot of these scooters and performance parts for them making access to good pipes not that hard to find!
1542608498954.png
pipes like this can be found from China,Italy,Germany,France,England and more pretty cheap this one is only 60 bucks cheap China sh*t but it still works quite well and better made stuff just works better again and last's longer.
 

Vikingimike01

Active Member
Joined
Jul 1, 2018
Messages
768
Yeah, I guess that's not that much. I'll try that, or get an used one. Should I go for 50, or 80cc scooter pipe?
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
3,103
Yeah, I guess that's not that much. I'll try that, or get an used one. Should I go for 50, or 80cc scooter pipe?
Most scooters start out at 50cc and the end user can upgrade it with a big bore kit that brings it up to 70cc so stock pipes are meant for 50cc and performance pipes tend to be for the 70cc upgrades and this works real well for our engine's.
 
Top