Kx85 install

[Mad Willy]

Anyone out there install a kx85 on 40mm studs? What's the skinny on this install? Kits avail? Pure fabric job?

 

[GreasyChris]

Crmachine sells this but you'll probably still be fabricating it to fit your bike.

CR Machine | CR Machine

crmachine.com

 

[Member 30059]

Yep ive done a few. They are oriented the wrong way for our flanges and only work as a "belly pipe" it needs a fabbed flange and needs to be cut and welded upside down basically.

Like this

I definitely dont suggest using one on a stock cylinder though. Its too big for a 66cc, the power band hits hard but is very narrow and high and youll likely never hit it

 

[HumanPerson]

here is a cut up and reconfigured to fit the bike KX65 expansion chamber :

Here is the Junker Columbia Klunker with KX65 pipe reconfigured and modified to use the SBP pipe first divergent cone.
With the 40th rear sprocket it has crazy low rpm torque and hill climbing power like crazy.
Tops out at WOT around 34'ish and just pulls like a clydesdale

View attachment 90804

View attachment 90805

 

[FNTPuck]

Lol first I thought you meant who put a KX85 motor on a bicycle...I was ready to say I hope you can fab! For the pipe, it can be done but like stated its really big for a stock bore chinagirl.

Yep ive done a few. They are oriented the wrong way for our flanges and only work as a "belly pipe" it needs a fabbed flange and needs to be cut and welded upside down basically.

Like this
View attachment 91688

I definitely dont suggest using one on a stock cylinder though. Its too big for a 66cc, the power band hits hard but is very narrow and high and youll likely never hit it

You can do a kx85 as a top pipe but it is more difficult. Needs to be sectioned into 3pcs and then fix the angle of the stinger since it kicks out a lot, here is one during mockup on my test motor before I cut the tabs off and primed+painted it.

I agree its too big for most builds - on my ported triple40 with a back to back comparison with an RM85 pipe the RM85 only lost ~1.5-2mph top end vs the kx85 but had noticeably stronger mid range and was more fun on the street. That is also after fixing the KX85s massive stinger which needs to be reduced for our bikes tiny exh port. I'd say the 2mph up top is worth the trade-off of the extra mid range of the RM85 IMO but to each his own.

For most chinagirl commuters an RM85/KTM65 is perfect.

 

[Mad Willy]

Interesting.. thank you all. The setup I'm dropping this on is a yd100 Ive modified.. cut in a window on the piston, and added a reed valve. Using a mz65 with great results, but hoping to push it a bit farther with this pipe. FNTP, nice work. It's likely I will move in the same direction by sectioning it up and resetting everything. Any chance youd be interested in doing one for profit? I might go find an rm85/ktm65 for comparison.
Thanks for the link, Greasy.. unfortunately looks to be out of stock but I'll drop them an email to see if they are going to be replenished. Thanks All.

 

[FNTPuck]

Interesting.. thank you all. The setup I'm dropping this on is a yd100 Ive modified.. cut in a window on the piston, and added a reed valve. Using a mz65 with great results, but hoping to push it a bit farther with this pipe. FNTP, nice work. It's likely I will move in the same direction by sectioning it up and resetting everything. Any chance youd be interested in doing one for profit? I might go find an rm85/ktm65 for comparison.
Thanks for the link, Greasy.. unfortunately looks to be out of stock but I'll drop them an email to see if they are going to be replenished. Thanks All.

I did for a while and sold a few online and locally but stopped because honestly the time it takes to get one "right" would mean charging too much and it got to be not worth it.

I like to take my time and get the angle just right, nice tight tuck to the frame, still be able to remove head without pulling off pipe, cut off and grind smooth all the unused tabs and mounts, replace the stinger with a proper sized one, test ride for leaks, then clean, prime, and paint them which is a solid 2day/weekend job which isn't worth the $100 or so profit per pipe. If I was just chopping the header and making it fit like some of the facebook guys do its a different story, but I'm not gonna sell something that I wouldn't find acceptable myself.

 

[Street Ryderz]

Yep ive done a few. They are oriented the wrong way for our flanges and only work as a "belly pipe" it needs a fabbed flange and needs to be cut and welded upside down basically.

Like this
View attachment 91688

I definitely dont suggest using one on a stock cylinder though. Its too big for a 66cc, the power band hits hard but is very narrow and high and youll likely never hit it

Only as a belly pipe huh? yet there are hundreds of people that use them fitted normally.

 

[Mad Willy]

Thanks, FNTP. Worth the ask. I will give it a go and see how it goes.

 

[Member 30059]

Only as a belly pipe huh? yet there are hundreds of people that use them fitted normally.

That was established already