Carb and exhaust ideas for vintage chopper.

#1
Hi, keeping the project chopper !! I need a carb, linkage, and also the linkage that goes on the side cover... BUT I read that a PZ16 carb works better, better throttle range and control, and I don’t have to worry about all the linkage and governor. Price would be the same or cheaper since I don’t need the linkage, has anyone run one on the HS 40 ??. Any idea on exhaust? Would like something that goes out to the back or way down to the side like a old school HD chopper . Thanks
 

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cfh

Well-Known Member
#2
i have an HS40 on my Arco chopper with a pz16 carb. there wasn't a lot of room for the carb, so i used the existing manifold, and modified the carb to fit it. On the exhaust i made one. it's far from stock but it looks cool. To be honest, it's way too much engine for this thing. If you hit the gas too hard it wants to wheelie out from under you, putting you right on your butt, and the bike goes flying!
http://www.pinrepair.com/minibikes/p/arco1970_easyrider_mine1.jpg
http://www.pinrepair.com/minibikes/p/arco1970_easyrider_mine2.jpg

Here's my Ruttman chopper with a stock exhaust. This also has an HS40 but with a stock carb. you can see it barely fits. this bike doesn't want to kill you so much...
http://www.pinrepair.com/minibikes/p/ruttman_grasshopper_chopper1.jpg
http://www.pinrepair.com/minibikes/p/ruttman_grasshopper_chopper2.jpg
 
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#3
i have an HS40 on my Arco chopper with a pz16 carb. there wasn't a lot of room for the carb, so i used the existing manifold, and modified the carb to fit it. On the exhaust i made one. it's far from stock but it looks cool. To be honest, it's way too much engine for this thing. If you hit the gas too hard it wants to wheelie out from under you, putting you right on your butt, and the bike goes flying!
http://www.pinrepair.com/minibikes/p/arco1970_easyrider_mine1.jpg
http://www.pinrepair.com/minibikes/p/arco1970_easyrider_mine2.jpg

Here's my Ruttman chopper with a stock exhaust. This also has an HS40 but with a stock carb. you can see it barely fits. this bike doesn't want to kill you so much...
http://www.pinrepair.com/minibikes/p/ruttman_grasshopper_chopper1.jpg
http://www.pinrepair.com/minibikes/p/ruttman_grasshopper_chopper2.jpg
Very cool choppers !! How do you like the pz16 vs the stock carb ??
 

cfh

Well-Known Member
#9
I haven't ordered a PZ16 in a while. But on the ones i bought back a year or two ago with left side choke, no jetting change needed. I have upgraded my buys to the PZ22 (left side choke.) The crop on ebay right now is pretty good as the jetting is perfect for my HS40 and HS50 engines. (Back a year ago the PZ22 required a main jet change.) I run with no governor and a hot cam. but i'm pretty sure that does not matter.

what i have found is the supply of these china carbs is pretty unreliable. So when i find they are selling a particular variant that works well, i buy a crapload of them! I think i have 15 of the PZ22 carbs on my shelf right now, because they awesome (at $12 each, it's not much of an investment.) Back 6 months ago the PZ22 sucked. I couldn't get it to jet right no matter what i did. And before that (year ago), the PZ22 was awesome but required a 90 to 95 main jet (depending on the motor.)

i don't understand this, but it's how the world of china carbs works.
 
#10
I haven't ordered a PZ16 in a while. But on the ones i bought back a year or two ago with left side choke, no jetting change needed. I have upgraded my buys to the PZ22 (left side choke.) The crop on ebay right now is pretty good as the jetting is perfect for my HS40 and HS50 engines. (Back a year ago the PZ22 required a main jet change.) I run with no governor and a hot cam. but i'm pretty sure that does not matter.

what i have found is the supply of these china carbs is pretty unreliable. So when i find they are selling a particular variant that works well, i buy a crapload of them! I think i have 15 of the PZ22 carbs on my shelf right now, because they awesome (at $12 each, it's not much of an investment.) Back 6 months ago the PZ22 sucked. I couldn't get it to jet right no matter what i did. And before that (year ago), the PZ22 was awesome but required a 90 to 95 main jet (depending on the motor.)

i don't understand this, but it's how the world of china carbs works.
Thanks for the info! I understand these carbs only work well with a free flowing exhaust, I’m going to build my own but would still like to quiet it a bit. Is there a muffler that I can add to my system ? Maybe like a straight through cherry bomb or thrush type for a car? Thanks
 

cfh

Well-Known Member
#11
slide carb will still work great with a stock exhaust. just you don't get all the benefit of the slide carb with stock style exhausts.
 
#12
slide carb will still work great with a stock exhaust. just you don't get all the benefit of the slide carb with stock style exhausts.
Thanks, so is just a straight pipe (open header) the best for performance ? or is there a muffled system that will work good also? I was planing to make a 1/2" smooth pipe right off the motor angled down about 12-15" with a long style straight 1/2" muffler off of that.
 

Doc1976

Active Member
#14
1/2" is too small for exhaust. even 3/4" is kind of small but workable. the ideal tube size is 7/8" for exhaust.
This. I use 7/8 for my briggs motors, which works out well since my frames are built of 7/8 and that's the only size die I have for my bender. I just use straight pipe no muffler.
 
#15
Hi, keeping the project chopper !! I need a carb, linkage, and also the linkage that goes on the side cover... BUT I read that a PZ16 carb works better, better throttle range and control, and I don’t have to worry about all the linkage and governor. Price would be the same or cheaper since I don’t need the linkage, has anyone run one on the HS 40 ??. Any idea on exhaust? Would like something that goes out to the back or way down to the side like a old school HD chopper . Thanks
 
#16
If your looking for the best overal performance. A mikuni vm is the best carb to be had. I run a 18mm on my mini with a open velicity stack. For exhuast I built that like all I build starting with a 1 inch header pipe and smooth radious bend back from the head.The pipe is only 11 iches long before it enters a adapter pipe that flares out to fit a 3 inch supertrapp muffler. One of the best muffler set ups ever made for any engine that will not be turbo or blown.They sell at summitracing for 56.00 and its fully tunnable.I didnt want to think it would work since its good for up to 100 hp.My engine now has 7 hp after all the mods and thats a dyno number. The one thing I can fast tell you for the exhuast style your after.Is length of pipe wont do anything good for performance. Id stick with one no longer than 18 inch at max and the less smooth bends over just one wont do you anything good ether.Then thats up to you I only know what I like and its performance period. At 65 years old Im good at getting it from anything I run.What else I can tell you about this muffler.Is it isnt real quiet but is better than any straight pipe being about obnoxious from any engine as small as all of whats in most mini bikes.So to run this setup takes care of it well enough and still sounds real good when in fact it sounds alot better.You can also use this muffler to tune from if you want to quickly richen or lean out the mixture.You simply add or remove one or more of the disc. Making this a win win setup. By running a mikuni carb you wont have any need for any linkage to get in the way or screw up,Simply run a throttle cable to the carb and your done.The return spring the carb works with takes care of the cable return. And I promise you wont find any better but alot worse performaing carbs than any mikuni. Thats why anyone that races or wants performance from any motorcycle turn to this brand of carb.Mill your head and exchange the valve springs advance the timing maybe port and polish.And your engine will fly like my 79cc predatore sure does.
 
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