MOPED ARMY

Just saw first and last pictures, nice work. All mobys ive had were smooth except when the mounts go out then its a jerky shaky thing. Id weld up some engine mounts n that springy hook thing. Or start balancing stuff magneto pulleys etc. Amazing how much energy lost to vibration instead of smoooothness.

Cheers Pat, I'm probably being thick here but you lost me on "that springy hook thing"?

Good shout on balancing the external bits, hadn't thought of it but if the pulley is out that could cause serious vibration.

Cheers Stephen, I'll pop these guys out and see what space I have to play with, iirc they're 6mm thick.

Any clue what rubber would hold up to that kind of heat?

As for engine balancing, I think that might be too overboard.....its only mopeds right? And can you really balance a single anyway?

You could buy some ductile butyl rubber and mold it around the head mount bolt. Slide it into the head then use a chopstick or somthing to cram the rubber in tight. Then bake at 350 for a while to vulcanize it. Boom custom fit rubber isolator

I'm almost certain it was butyl....we used to fool around with in school, then vulcanize the parts in an oven....you could work it like clay

Ok, so decomp is useless when it comes to plug chops, lesson learnt but at a cost of a soft seize 😢. Shoved an endoscope down the plug hole and there are some marks on the bore, won't know more til I pull it to bits. Soft seized at full chat so I'm OK down low but lean at wot, before really pushing it further I'll take up the offer I've had to put it on a dyno and dial it in exactly.

Question tho. I'm new to all this, is it OK to keep a 2 stroke engine pinned if you've got it jetted right??? I'm running a bit retarded (but people have said that for years) so I thought I'd be on the safe side. Any help guys and gals would be appreciated, digging for your wisdom here, how do you roll at wot? Let off and back on or never push right to the limit, I know it's the most newb question to ask🤦‍♂️

Yeah getting that SHA dialed in so it can idle nice and lean but be rich enough at the top with a smooth delivery curve is the key. Have you already opened up the upper hole in the brass tube?

One thing that could also help is ensuring a stable pocket of air that the carb is drawing from at all speeds. Helps make the carb more consistent at all ranges. Since the engine doesn't pivot like most Mobys you could potentially fabricate an air box inside the frame behind the carb. There are formulas you can search for that estimate the ideal volume based on bore size etc.

Thanks Mike but no I haven't, tbh I'd completely forgotten about that bit🤦. Guess I should order some jet drills sharpish, what sort of range should I be looking for, and it'd be great if you could suggest a starting point (did search but didn't find much)?

I had a similar thought, I was thinking about whether I could make up a version of a JBOT bottle. Space is a tight with these gusset plates and to put the belt on you pull the engine back so far that the filter hits the plates.

The air should be pretty stable there, the chain cover completely covers the filter, I might try and work something out but so far I've drawn a blank. (edited)

Sha tuning is easy just keep in mind that rather than going down a jet you can remove a screen from the filter pack and add some more air to the mix. And always jet for top speeds. You might end up a little muddy at the bottom but you wont seize at your top.

Looks rad! Have you considered fabbing up a little rectangular cable management doohickey, maybe from that mounting point for the crossbar? It’s tough with tall bars like that but I think a little cinch there could clean up the look while still allowing full range of movement

Thanks guys! I did try feeding the cables through the little light bracket at the bottom of the bars but it didn't look right. Hadn't thought of making something to cinch them to the lh and rh of the bars, I'll have a play around 🤔.

Also old tyres were 16x2.125 not 1.25. New tyres have geared it up a bit but don't have a GPS speed, I had finally found a 36t rear sprocket to replace the 38t but I'll hold fire at the moment.

If anyone else is stuck, puch maxi sprockets are an exact fit, you just have to space them off the hub a bit to miss the spokes, the time I've wasted looking for a nos wisp sprocket...

I took it for a run this afternoon and it's running great, flying through some twisty country lanes, should have been paying more attention to the temps as it nipped slightly (181°c / 358°f). I'll upjet to a 76 and try that🤷.

Hmm it shouldn't be seizing at those temps, sounds like you might need to back off your timing a bit. If going richer doesn't bring the temp down, it's not your problem. Turn whatever knob makes the biggest difference.

An air leak, while possible, seems unlikely based on the fact that your build quality is excellent and the larger jet didn't immediately make a difference, you could keep going bigger and see what it does but if the timing too advanced, no matter how rich your piston will still be hot and seize

Thanks for the advice, I'll try retarding the timing back a bit first and then change the sprocket, that way I'll know which makes the most difference.

Cheers Graham, that makes sense, I'll try timing and a serious diet then.

Could someone school me on what they think might be going on here👇.

I'm still trying to tune my ear into 2t engines, sounds like it might be 4 stroking but the plug chops look on the lean side. This was a warm up run so engine is still cold (100°c) and lambda sensor crapped out so testing was aborted.

9:1 compression

Ngk BR6HS

16:16 dellorto (full mesh filter) 76 jet

40:1 E5

Timed 19° btdc

I'd like to get it running better before I try this again, any help/advice/pointers would be greatly appreciated!

Cheers Iain! Sketchy is pretty generous, hand signals are out of the question, instead I point with my legs🤣. If you ever get chatting to your brother-in-laws neighbour, advise changing to BMX tyres, the difference is amazing!

Nice to hear from another UK mopeder👍, are you part of the Lancashire slow riders?

NO, and I'm moped free. always had one on the go though as a rule. Last one was a Tomos and before that a Honda PC50 which I had for donkeys years. Also had a Vespa Ciao and a couple of Yamaha geared 'peds.