Dyno Tomos Build - Lil' 60+mph A35 ripper.

(Long post, I have a ton of progress pics that I will slowly add but for now just posting the nearly finished result. Accidentally posted in Performance section but its a build overview so should be in General. Can't find a way to edit or delete posts, can a mod please delete it?)

Figured I'd post a project I'm almost done with on here for all you moped heads. I traditionally build cars and motorcycles, but have spent the last 3 years or so tinkering with both 2stroke and 4stroke motorized bicycles. Over a year ago a buddy with a Tomos that sat for a long time was moving and needed to get rid of it, so knowing absolutely nothing about it I picked up a complete '92 for real cheap since the motor was seized up and it didn't run. I had no idea what I was gonna do with it until about 2 months ago, when I got the idea to make a motorized "brother" for my '96 GT Dyno bicycle that I have had since new in 96 as a kid. I still have a bit to do to it, but my original goal of a fun little 60mph ripper has already been achieved and I figured some of you guys might get a kick out of it.

Started with a 1999 GT Dyno bare frame I purchased used online. Went with the 99 since it looks close enough to the 96 on the surface, but is way cheaper since the 97 and older are US made frames that are much more expensive and harder to find. Cut off the brake mounts and smoothed them down. Stretched it 2" behind the seat post and widened it 1/2" to clear a DOT moped tire, then on the front end lengthened it 1" more and cut off the stock head tube and moved the complete Tomos front end to it while adding quite a bit of rake - took it from the nearly vertical BMX head tube to 26* to keep it stable at speed and bring the trail numbers to a safer level.

Cut down the bottom bracket and welded in some motor plates, which I boxed for strength and surrounded the seat post with a notched area on the back to mount the rectifier and flasher relay. Welded on some tabs for the axle adjusters to keep the wheel from pulling forward, and a tab for a steering damper, cooked up some custom decals on my vinyl plotter, and that about wrapped up the frame mods.

(will post modded+primered frame pic here)

For the motor, the jug was rusted out and the points system was stuck so I headed over to Treats and ordered the 45mm alukit w/ single ring piston and converted the old points setup to the A55 starter+flywheel and upgraded to a Parmaket CDI to pull some timing up top since it will be a high rpm build (aiming for ~11k once I start tweaking the port map). Also picked up a Jammer 1st gear clutch, and installed it with the medium springs along with a red spring in the 2nd gear centri to hold 1st gear longer. Kind of bummed about the physical gearing limitations, but will work with what I got lol.

Intake is a custom piece that I made by cutting the mounting flange off the stock intake at the widest point, then welding a much larger 4pedal reed box setup to it with a 3d printed stuffer to keep velocity up. It would never fit on a Tomos frame, but since I was modifying the frame at the same time I was able to place it in a way that would make it work. Carb is just a simple and cheap PHBG 19mm with a K&N, currently jetted rich for break in so there is some slight 4stroking when cold. It mostly cleans up after a lap or two around the block, but once I get some miles on it I will drop 1-2 jets on both the main and the slow to start tuning for power.

For the pipe, instead of a long header jog style pipe that favors mid range, I modified a YZ85 dirtbike pipe that screams up top. The Jammer clutch slips right into grabbing around 5k, the pipe starts to hit around 6500rpm, and pulls surprisingly hard to 10k+ rpm. Currently with stock 26t front sprocket and 20t rear, it hit 56mph before I left off for an intersection. Expecting ~65mph with a 30t front once I clearance the case for it...not too bad for a stock jug IMO, might be able to squeeze 70mph out of it with port work. Complete bike ready to ride is 89lbs, so a little over 20% lighter than a Tomos assuming 115lbs(not sure if thats dry or wet weight for the Tomos since I didn't weigh it before chopping it up lol).

That's about it...any questions or suggestions if I did something stupid let me know LOL. I have a fair amount of 2stroke knowledge from dirtbikes and cheap chinese bicycle engines, but this is my first moped engine so it took a lot of research.

Here is a quick vid from last week before I installed the axle adjusters and stinger brace.

https://drive.google.com/file/d/1-p7tf3Q7gGFy0IHMI4APSbgGF1Hgj-mz/view?usp=sharing

Will add more build progress pics from bare frame to completed bike once I get em uploaded. Braap braap.

YZ85Pipe.jpg

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

So fucking awesome! Love it!

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Damn, 60 on a BMX is no joke. That's one heck of a wild build. Nice work.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

> Graham Motzing Wrote:

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

> Damn, 60 on a BMX is no joke. That's one heck of a wild build. Nice

> work.

> Stephen Keller Wrote:

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

> So fucking awesome! Love it!

Thanks! It was a lot of fun to build and I am super happy with how its turning out.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Was curious if anyone else had that idea as well. Bet it hauls major ass.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

I think Will made an express BMX and there was another more Express than BMX in Buy/Sell a bit ago, nothing new under the sun.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

> Puck FNT Wrote:

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

> > Graham Motzing Wrote:

>

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

>

> > Damn, 60 on a BMX is no joke. That's one heck of a wild build. Nice

>

> > work.

>

> > Stephen Keller Wrote:

>

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

>

> > So fucking awesome! Love it!

>

> Thanks! It was a lot of fun to build and I am super happy with how its

> turning out.

YW, mad skills to build that, you going to get a tail light and make it street legal, or just race it?

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

It's getting a tail light setup and I'm thinking about a plate for it as well. Mainly so I can test it and dial it in more without worrying about getting pulled over lol.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Please be careful. Your craftsmanship is unquestioned, but that thing does not look at all like a conventional motorcycle. A motorcycle meant for high speed travel looks like a motorcycle for good reasons: the steering geometry, the center of gravity, the suspension, the tires, the wheels, and the brakes are meant for that kind of service, for roads are not always kind.

I suffered some serious injuries on a motorized Schwinn bike last October when I hit a poorly-maintained manhole cover and went sailing over the handlebars. Broke a collarbone and my neck, but I've recovered completely. The helmet--a silly bicycle helmet--saved my wretched life; half of it was scraped away on the pavement.

I've since purchased a real moped--1984 Trac Clipper, weird to work on but built like a tank--and I wear a real motorcycle helmet thereupon.

Mark Kinsler

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Tweaker trash /

Yea about to say I think 30mph is cool! It looks really cool it doesn’t need to go braking speed records

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

We need more pictures!

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Peugeot and mbk both made very rare BMX 'peds but they are pretty slow

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

> Mark Kinsler Wrote:

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

> Please be careful. Your craftsmanship is unquestioned, but that thing

> does not look at all like a conventional motorcycle. A motorcycle meant

> for high speed travel looks like a motorcycle for good reasons: the

> steering geometry, the center of gravity, the suspension, the tires, the

> wheels, and the brakes are meant for that kind of service, for roads are

> not always kind.

>

> I suffered some serious injuries on a motorized Schwinn bike last

> October when I hit a poorly-maintained manhole cover and went sailing

> over the handlebars. Broke a collarbone and my neck, but I've recovered

> completely. The helmet--a silly bicycle helmet--saved my wretched life;

> half of it was scraped away on the pavement.

>

> I've since purchased a real moped--1984 Trac Clipper, weird to work on

> but built like a tank--and I wear a real motorcycle helmet thereupon.

>

> Mark Kinsler

Thanks for the heads up and you are correct! Normally a bicycle becomes unsafe around the 35mph mark. I have done the whole department store bike with a motor thing and have broken pretty much everything possible on them - rims, spokes, hubs, frames, chains, etc. Over time you learn what works and what doesn't, and after replacing so many broken bicycle parts over the years I don't even use bicycle parts on most of my builds anymore - either custom, moped, or motorcycle. I actually have a big bore Briggs 4stroke on a stretched beach cruiser that is significantly faster than this bike as well. I know how to calculate rake and trail for proper steering geometry, I install hydraulic steering dampers to prevent tank slappers at high speeds on any bike I make that does over ~45mph, and know where and how to reinforce key spots on the frame to hold up to the increased abuse. Still not saying its "safe" and I wouldn't recommend others to try it, but I'm not just throwing motors on stock bicycle frames and hoping for the best :). This frame has been reinforced and modified where necessary, has proper rake, adjustable steering damper, DOT tires rated to 62mph, strong #41 industrial chain with perfect laser aligned sprockets, all parts properly lubed and serviced, new head tube bearings, brakes cleaned and adjusted, etc. Center of gravity is low thanks to the low and centered motor, and weight distribution is pretty close to 50:50. It feels very planted and stable at speed. Since you never know though, I also wear my full face motorcycle helmet when riding - even if I am just staying in the neighborhood.

Still wouldn't call 60mph on anything home made 100% safe, but I do take more precautions than most :). If the stock sealed bearing Tomos wheels are an issue though, I can replace them...I assumed they would be OK if balanced with good tubes and tires @ 65ish since I couldn't find any examples of them failing, but like I said its my first moped build and I am always open to learning! Wouldn't be hard for me to lace up some custom 17" wheels with 10ga spokes and get some additional tire OD at the time time to make up for the gearing limits lol. Could upgrade to disk brakes while I am at it!

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

I'm all about the bmx race-peds. Cool bike, nice work.

Here's mine

IMG_20200309_154521.jpg

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

> baird co Wrote:

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

> I'm all about the bmx race-peds. Cool bike, nice work.

>

> Here's mine

Badass, I love it!

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

derek from black pipes moped gang 🌧 /

Very sick

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

quality chromo tubing is without a doubt stronger than whatever shit quality stamped steel tomos used

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Since I can't leave well enough alone, I am pulling the motor off already to do some work to it (barely kept it stock for a week lol). The jug will be ported, and case will be split to weld on some material around the transfers to enlarge them in preparation for a potential future 47mm Gila build. For now, I will do the welding and enlarge the transfers, but will leave the bore alone and stay with the current 45mm alukit setup and port it out for now. Mostly just enlarging the transfers slightly, widening the ports a little, and blending them - not messing with the port timing much since I love the power delivery for this light little bike...maybe a slight increase in transfer port duration/entry angle to try to get a bit more rpm out of it.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Have a Gila 47mm setup on the way. Thinking I may have to up the carb to a 21mm now lol.

Re: Dyno Tomos Build - Lil' 60+mph A35 ripper.

Ϫ‡☄ಬ∞ ƀƖḬƝƊ ƤǂƿƎ ∞ಬ☄‡Ϫ - Hoke from Black Pipes Moped Gang /

> Ryan Graeme Wrote:

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

> We need more pictures!

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