70cc Puch Maxi top end?

Hey guess, been a while since I've had a bike, but picked up a '78 Maxi in September. Did a complete rebuild (bottom and top end) but I feel like I should have some more top-end speed. Currently hitting 35mph gps'd. Here is my setup:

- 70cc treats kit

- 15mm bing clone with 75 jet

- Proma circuit pipe

- New bearings, seals, stuffed crank

- 3 shoe 6.4 jammer clutch

- 15x45 gearing

The proma circuit is supposed to be a low end pipe, and I bought the jammer clutch to improve low end, but acceleration isn't amazing for 15x45 gearing. I read a lot of you guys are hitting 45 on similar setups with 17x40 gearing, but I can't imagine my acceleration being slower. I ride in Boston so I do a ton of stop and go riding and need good low end, but would love to be in the mid 40s for top speed. I've seen tomohawk mopeds videos on youtube when he's testing customer clutches or a reeded 70cc kit bike and those things fly. Any tips/ suggestions? Thanks!

Re: 70cc Puch Maxi top end?

Overpriced Parts /

Pipe tops out at around 8k with that setup so horrible gearing, not jetted/tuned/timed correctly, that clutch not needed with that low rpm pipe for a stock 2 shoe with thick springs would work fine,

I’m sure you’re not base spaced 3 mm and decked 3mm or have a 3mm counter sunk head either which is needed for treats kit as well as casematched right, all in all your missing 10 mph easy,

Re: 70cc Puch Maxi top end?

Dirty30 Dillon /

You are over-clutched for that pipe.

Re: 70cc Puch Maxi top end?

Stock two or three shoe is all you need for clutch.

Re: 70cc Puch Maxi top end?

P.S. use blue springs and weigh the arms and adjust them so they weigh the same on the big end. get a Digital Fishing Scale to help adjust the clutch springs and you should be good to go.

Re: 70cc Puch Maxi top end?

I had the stock 2 shoe clutch with stiff springs and my acceleration wasn't great, so I bought the jammer thinking it would help. In terms of base spacing 3mm, do I just need to add an additional base gasket? Or do I need to do more than that?

I'm tuned pretty solid, but not quite sure on the timing. It starts right up and runs great, just not as powerful as I had thought.

Sounds like I need to add a base gasket then - anything else?

Re: 70cc Puch Maxi top end?

Overpriced Parts /

> Kyle Washburn Wrote:

> -------------------------------------------------------

> I had the stock 2 shoe clutch with stiff springs and my acceleration

> wasn't great, so I bought the jammer thinking it would help. In terms of

> base spacing 3mm, do I just need to add an additional base gasket? Or do

> I need to do more than that?

>

> I'm tuned pretty solid, but not quite sure on the timing. It starts

> right up and runs great, just not as powerful as I had thought.

>

> Sounds like I need to add a base gasket then - anything else?

With timing and turning there’s so much you know nothing about I suggest you look at wiki

Re: 70cc Puch Maxi top end?

Ride it over to my house and we can have a look at it if you want.

Re: 70cc Puch Maxi top end?

I would say I'm pretty knowledgeable with timing and tuning compared to an average person. Tuning is not an issue, but not sure about timing. I timed at 17 degrees before tdc, but not sure of how to confirm that. I guess I could buy a timing light, but it sounds like the treats cylinder spacing could be my issue. Anyone else have more info about the treats cylinder spacing?

Re: 70cc Puch Maxi top end?

Where you located?

Re: 70cc Puch Maxi top end?

Did you case match?

I have the same kit, case matched. Treats hi comp head. I did not raise my cylinder. I installed it as it came. Dellorto PHBG 21, techno boss pipe. Stock clutch with kickstart springs, 2.5 turns in from flush. Timing 14* BTDC. 16 x 45. Eats hills, and does 45 easy.

You’re not tuned/ timed right. Do what was suggested, and spend some time in the Wiki learning how to tune your moped.

Re: 70cc Puch Maxi top end?

Dirty30 Dillon /

Yeah, I have installed 4 or 5 of the treats 70 PP kits and none of them required anything other then minor base gasket thickness adjustments

Re: 70cc Puch Maxi top end?

I'm running the same setup on my e50 other than the stuffed crank (shoulda bought it) mine runs good, does 35 no problem pulls to about 45-47 on flat ground, itll do 35 up decent hills perfectly fine as well. Running a 2.17 atomizer, 82 jet, needle in third from top clip groove, timed at 17° . Nearly keeps up with my buddies 70cc reed cylinder tomos.

Re: 70cc Puch Maxi top end?

Wow, I'm jealous! Sounds like I should be hitting low to mid 40s no problem.

Yes, I case matched when I rebuilt, forgot to mention that. I'm running a 75 jet, clip 3rd setting from the top, and a 217 atomizer jet.

After spending a few hours reading about squish, it sounds like that is probably my issue. Someone on treats mentioned that they had to use no head gasket and a thinner base gasket with that kit. I'm using the hi hi comp head as well.

In terms of timing, how can I ensure that it's correct? Are plug chops the only way?

My powerband doesn't hit as hard as a strong 2 stroke should, so I think the squish is affecting my compression. Would that also explain why my temps don't usually get above 310?

Re: 70cc Puch Maxi top end?

Probably timing or jetting, along with clutch tuning. Seems like everyone had some good suggestions. I would not worry about deck night or squish right now if all the ports are fully opening. What springs are you using with that clutch. The weakest ones might be the best. It may not be fully engaging. Seems like lots of people in your area are willing to help. I would see what they have to say in person.

Re: 70cc Puch Maxi top end?

Read this page on timing from the wiki.

https://www.mopedarmy.com/wiki/Puch_timing

You need to do it with a timing light, and you’ll need to Dremel the slots on your stator plate.

Btw, plug chops are to check air/fuel mix, not timing.

Re: 70cc Puch Maxi top end?

Yeah, and like Eric said, it’s probably not your squish. Worry about simple stuff because something simple is holding it back- Ignition(timing, new Bosch points), clutch, carb tuning, or air leak.

Or a dragging brake ;)

Re: 70cc Puch Maxi top end?

My 2 shoe clutch had the stiff springs & clutch brace set to 2.5 turns in from flush, but my acceleration wasn't great at all. Being in Boston, I need great low-end, hence my pipe choice. The jammer clutch I'm using has the softest springs installed. Clutch seems to grab pretty nice, but has a lot of slippage.

I'm surprise that timing alone could be the reason for all of this power loss and not the squish height! I feel like carb is properly tuned as I see a lot of people with similar setups running between a 72-80 jet. I don't have any airleaks as I sprayed it down with carb cleaner and there was no change in idle.

Sounds like I need to order a timing light to check for timing. If i'm maxing out my temps at 310, would that suggest my timing isn't advanced enough? And do you run a head gasket or should I go no head gasket?

Re: 70cc Puch Maxi top end?

I am a firm believer in a head gasket with all the nuts torqued to specs.

Timing is going to affect top speed, acceleration, throttle response, head temps and jetting. If it fires too early your going to heat soak the head and probably seize or if it fires to late it is going to not properly burn fuel which would lead to poor performance. I would read up about timing and get a light. I kept buying cheep lights off amazon, but they kept burning up. I went to the auto parts store around the corner and grabbed a decent light off the shelf, blew the dust off it and had the parts guy ask me what in the world I needed that for. However it was worth the investment. You have to listen to what the bike wants. Just because some people run a range that is usually a good starting point but every bike is different. You might a couple Jets higher or lower than a person with the same setup. You would be surprised how much more power a properly timed bike with correct points gap will have.

Re: 70cc Puch Maxi top end?

Thanks for the info. I'll be taking a trip to autozone after work to pickup a good light. I ride 2 stroke dirtbikes and those things are fast as shit. Pipe powerband hits hard, and they rev to the moon. The feeling on my maxi isn't quite the same. My pipe powerband starts hitting hard and then never keeps going and just flattens out. I don't have the peppy torque in the power band range that a normal 2 stroke would have, so I'm gonna check timing and hopefully that's the problem.

These small little motors are a lot more complex than I thought when it comes to getting them perfectly dialed in!!

Re: 70cc Puch Maxi top end?

Overpriced Parts /

> Kyle Washburn Wrote:

> -------------------------------------------------------

> Thanks for the info. I'll be taking a trip to autozone after work to

> pickup a good light. I ride 2 stroke dirtbikes and those things are fast

> as shit. Pipe powerband hits hard, and they rev to the moon. The feeling

> on my maxi isn't quite the same. My pipe powerband starts hitting hard

> and then never keeps going and just flattens out. I don't have the peppy

> torque in the power band range that a normal 2 stroke would have, so I'm

> gonna check timing and hopefully that's the problem.

>

> These small little motors are a lot more complex than I thought when it

> comes to getting them perfectly dialed in!!

Yes because they were designed to be a slow ass Mopeds that revved to 6500 if that,

Believe me I was a enduro/duel purpose/dirt bike runner and raced hair scrambles several times, always got a finisher pin,

mopeds are not off rode dirt bikes but I made many of mine close to that!

Re: 70cc Puch Maxi top end?

Yeah, they weren't designed to rip for sure haha. Gonna pickup a timing light in a few hours and hopefully get my ped running mint so I can ride it to work tomorrow. Wouldn't be surprised if my timing is off after reading the wiki, I did the old eyeball method with a plug stopper and timing tape. I'll update late tonight/tomorrow if I end up getting it worked on tonight. Really hoping the timing is my issue.

Re: 70cc Puch Maxi top end?

Update: bought a timing light last night and checked my timing today by following the YouTube video posted in the wiki. My timing was at 11* btdc. I adjusted it to 16* with the light and it started drizzling so I buttoned it up and took it out.

Acceleration is much better, but I still think there's some additional improvement available. Top speed was 36mph, so same as before. It feels like the pipe hits around 20/25 and then tapers off on the top end. I know it's a low end pipe, so taller gearing is needed for sure. During my 5 mile ride with some good WOT stretches, temps maxed at 330F.

Questions: I have a head gasket on, should I leave it and advanced the timing to 17-18* since I'm still running cool? Or remove the head gasket? Also, it's definitely not 4 stroking at top end with a 75 jet, so I was thinking of throwing an 80 in there. Should I leave the timing at 16 when tuning the carb? Or should I advance timimg first, test, and then tune the carb?

Thanks for the help so far, my timing was definitely off as you all thought! However, I still think there's some room for improvement

Re: 70cc Puch Maxi top end?

Logically , get the timing right first .

Not much use in painting a turd . ;)

Re: 70cc Puch Maxi top end?

Yeah, that is correct! Timing at 16* and I just swapped in an 80 jet. Also did crazy Wayne's bing slide mod to remove the low end bog.

Still doesn't have great power, in fact it was probably worse. My clip is 3rd from the top (2nd richest setting). I'm gonna try to down jet to a 72. The only hesitation I have is that it doesn't 4 stroke on the top end with the 80 jet. It almost feels like it's running lean, but doesn't get hot and actually ran better with a 75. Any idea what could be causing that?

I don't know how you guys get your peds dialed in and ripping to 45 with great acceleration, but all of the time I've spent on this thing with the rebuild and trying to get it tuned must be close to 30 hours. My ride time is probably around 1.5-2hrs which is very frustrating!

Re: 70cc Puch Maxi top end?

Learn how to read a plug .

It may just shorten your tuning time .

Re: 70cc Puch Maxi top end?

Yeah, you are just starting to tune now. Quit jumping all over the board. Make small adjustments. Do one thing at a time, and check results. You don’t have any time into that bike yet. Change jets a maximum of one or two sizes at a time, then test ride. Example, go from 72 to 74, and try it. Jumping from 72 to 80 to 75 is screwing you. Don’t adjust two things at once, like jets and needle, you won’t know what worked. One thing at a time, then ride. Recheck your timing according to the link I sent you. It may take a couple tries to get it right. I think you’re still off. Tiny adjustments to timing, jetting, and needle settings have big affects on these bikes because of their small engine displacement. If you’re off by one jet size or one needle clip setting, your bike will be a dog. A couple degrees too retarded, and you’re a dog. Not like a bigger bike where tiny adjustments aren’t as noticeable.

By the way, your 50cc or 70 cc moped will never compare to a two stroke dirt bike. It’s still a moped.

Keep at it, it takes time and practice, but if you’re patient, the experience will come and it will get easier.

Re: 70cc Puch Maxi top end?

Thanks Seth, I appreciate your help. I spent some time with timing and tuning today, and it seems like the Jets between 72-80 (72,74,76,78,80) all have almost the same feel at WOT, but acceleration varies slightly. I'm timed at 17*, and I settled on a 73 jet. No matter my jet (72-80), my top speed was always between 35-36mph. I have 2 questions:

1) does the proma circuit have a maximum rpm that it won't usually go over because it's a low end pipe? If so, that would make sense as to why my top speed doesn't increase.

2) I'm still running the 6.4 jammer clutch, but I feel like my old 2 shoe with the stiff springs might have had a snappier feel at takeoff. I know you guys said I'm over-clutched for my setup - is over-clutching on a moped similar to having too strong of a clutch on a car? I might toss my 2 shoe with stiff springs back in and see how that feels if you guys think I should go back to it.

Regardless, I have a 17 tooth and 40 tooth coming in this week. Going to go from 15x45 to 17x45 and see how I like it/if low end is still solid and what my top speed is. If I still want more top speed, I'll throw the 40 tooth on.

I've never ridden a properly tuned, kitted e50, nor have I ridden a bone stock one, so I really don't know how hard the Powerband should hit/how good my acceleration should be. 4 years ago I had a kitted tomos with a 2 speed, so it wasnt quite the same but it topped out at 48. I'm thinking that it's running really well and I'm just expecting a bit too much out of this little engine, but maybe I'm wrong

Re: 70cc Puch Maxi top end?

Man, I don’t get it. You should be doing way better than 35. I can get better than that with a stock top end, pipe, and carb, with stock gears, just by changing the air filter and tuning the carburetor. You should be low-mid forties easy, even with the Proma. It’s not a high revving pipe, only about 8,000 rpm’s, but still. I can’t figure out what you’re doing wrong.

I do think you’re a bit optimistic in your expectations, but it should be performing better than it is. You are definitely over clutched. Two shoe, with kickstart springs is my go-to for stock and mid performance builds. If you were closer, I’d give you a hand with it.

One more thing; you have a clone carb. The carb body is fine, but have you changed to genuine Bing atomizer & slide? Make sure you’re using good internals, because the clones are tough to tune unless you replace the guts. I see you said it’s a 2.17, I don’t know if a 2.22 would help, but you might try it.

Your timing is at 17* you said. That’s okay if you’re stock, but I’d rather see it around 14-15. But to do that, you’ll have to file/dremel the mounting screw slots in order to rotate the stator plate far enough. You’re gaining on it. Keep at it, you’ll get there. Just remember, small adjustments make big differences with an engine this small, due to the small volumes of fuel and air it consumes.

Re: 70cc Puch Maxi top end?

Thanks again for the helpful tips Seth!! I really appreciate it.

I also thought I should be hitting at least 40 with my setup, but if my pipe tops out around 8,000-8,200, then I am maxed out. According to the e50 gearing/rpm chart, hitting 36mph with 15x45 gearing equates to 8,000 rpms which would make sense considering my pipe maxes out at 8k. I'm gonna toss my 17 tooth on when it comes in, and see how that goes.

The one thing that's been really puzzling to me is that at WOT, I didn't feel a difference between any of my Jets. It feels like there should be more, but it does top out at 36. I've toyed with the idea of buying a vm20 since that's the carb I had on my old tomos and absolutely loved it, but it seems like there are a lot of people who use a bing 15 on reeded bikes with lots of success.

I'm getting to the point where I'm just going to suck it up and be satisfied with where it's at. Hoping the 17 tooth gets me above 40. Right now, it starts first kick every time, idles perfect, and has no air leaks. Not really sure what else I can do.

Because it doesn't 4 stroke on the top end, I did try upjetting to 85. This still didn't cause it to 4 stroke, but made it really rich at idle/low rpms. The one thing I haven't touched is the needle clip setting. I've left that at the 3rd clip from the top.

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