Two stroke tuning?

[Fladdem]

Any good places to start with somewhere to read up on it?

I often hear talk of squish bands and although I think I get it, I'm not certain but would like to know more. There's a certain moped calling to me in the garage.

Thanks!

Any tales of tuned smokers, bring this way too!
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Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[MarJay]

[MCN]

Swap out the original powerbands for something more use-able would be my first mod.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[stevo as b4]

A black art indeed!

You can have a fast two stroke engine with all kinds of cylinder head shapes and combustion chamber profiles, but it seems there's a whole load of variables that affect how you change things and set them up.

I've read loads of books, and wrecked loads of old motors messing with them, but the one thing I think I have learnt from reading about stroker tuning is that change one thing and it seems to affect everything else!

Without spilling the beans yet on my reckless recent spending, I've recently learnt that stuff like ignition timing is massively important on things like exhaust pipe design etc.

Oh my one and only big two stroke tuning tip is:

1, go in garage and get your Dremel tool out your toolbox, and then smash it with a hammer and throw it in the bin! It's only only safe thing to do!

[ScottT]

I've got both these books, great reads a bit dated now but the principal is much the same, they date from a time when people tuning their 2 strokes at home was a common practice.

https://www.amazon.co.uk/Performance-Tuning-Theory-Practice-Two-Strokes/dp/0854293299/ref=sr_1_5?ie=UTF8&qid=1441320533&sr=8-5&keywords=2+stroke+tuning

https://www.amazon.co.uk/Two-Stroke-Tuning-Roy-Bacon/dp/0851840396/ref=sr_1_3?ie=UTF8&qid=1441320533&sr=8-3&keywords=2+stroke+tuning

[robs321]

Graham File tuned a couple of bikes for me back in the 80s. I believe he is still down in Hythe waving his magic rifflers!

[MCN.]

Pay someone who knows what they are doing and buy the best exhaust and ignition system you can afford.

[tony_d123]

Before you do it, just think about what you will gain. if it's a moped, maybe another 0.5hp but lose bottom/midrange on a bike that is not blessed with loads anyway? Plus the reliability issues.
Blue printing and careful matching is good, hacking the ports can make it horrible to ride.
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Blackpool, Lancashire

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The exhaust is probably the most important part. Designing a pipe which exceeds the manufacturers effort is hard work.

A slight miscalculation to the chamber and it runs crap. An old team mate made his own (with the help of Gibson), at first it was very poor, after calculating again, adding around an inch to the main chamber added around 30% more power.

With the cost of a decent set of spannies now costing around £750, I always fancied having a go using some of the free software to work out cones etc. Unfortunately I don't have a tig welder and even my Mig skills are very basic.
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TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[MCN]

[Old Git Racing]

First rule of 2 stroke (or any) tuning is to make it like it should be, i.e. blueprinting it. The gains from doing this are surprising. On a stroker things like matching the ports to the liner, crankcase to transfers etc. Balancing the crank dynamically, Getting correct piston to bore clearance, using good rings with correct end gap, matching piston weights. Ignition that is correctly set and carbs jetted correctly. All easy enough (maybe not the crank). No losses doing this only gains.
Then start changing things. Gas flow the inlets, pipe change, jetting, programmable ignition, raise or widen ports, bigger carbs. Usually for a gain in one area you will lose elsewhere when you get to this level.
I did my own 350YPVS. Blueprinted motor, flowed ports all matched and knife edged, Banshee spec crank to rev higher, ignition from earlier model to let it rev, Wossner forged pistons with rebore to match each piston, Nikon pipes, gutted airbox with bored carbs. Don't know what BHP it does but it was good enough to do the last season I raced it unbeaten.
Theres no one big thing to tune a stroker, its marginal gains in a lot of areas and takes many hours to do it right, good tho when you start it up and hear and smell that 2 stroke goodness!

OGR
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2022 Tiger Sport 660 2019 Street Twin 2003 K3 gixxer 1000 1998 Srad 600 track hack

[MarJay]

[stevo as b4]

[Fladdem]

It's actually a H100 engine that I was thinking about, while it's on the bench, just begin by refreshing everything then minor porting, essentially removing any flaws to begin with, due to a lack of gas flow knowledge.

I have read project 60MPH with an MB5, if I recall they got about 55 out of it, so not bad, will have to look into the AR80.

Stan Stephens name is often mentioned next to two strokes.

with regard to the moped... why not? I know it's never going to be mental, but is more for fun. I would tinker with the CRM but I think the engine is just spot on where I like it as is, plus you can still buy barrels for the MT50 from europe for not stupid money.

Or go out and grab an MZ 250 to see what happens. No. I no longer have room for extra project bikes.
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Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

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[MCN]

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[picture_man36]

Looking at what you are doing, the H100 mod is the most effective. If you trawl EBAY.DE you can pick up a decent 80cc front and tail pipe which will work with your 100cc engine. I'm doing the same thing... I owned an MT@ 16... I've built one with a 60cc big bore kit which I want to do 50-55 & I've the bits for a second which will be a 100 cc sleeper. You've maybe seen the 80cc ? I've seen there's a 110cc big bore.. not sure whether this fits the H100 bottom end as its designed for the MT80.. You'll need the H100 carb, CDI etc... I'm going to use the H100 rear wheel on my MT to gear it up slightly. I've jacked the front and rear end up and spent stupid money on having the outer engine casings polished, fork legs, yokes etc as well as powder coating frame, wheels, handle bars all associated parts, paint and period decals. From a £90 field bike it probably stands me @ a grand!
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'The Picture Man'

[picture_man36]

AND if you are going to port & tune it.... give it to the professionals... I ran a TZR250 which was tuned poorly... it went like stink BUT ate pistons..... Have it blue printed and mildly tuned... thereafter you lose reliability... a H100 engine in an MT frame will get you 60-65mph pretty rapidly....
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'The Picture Man'

[stevo as b4]

I agree!
Adam is doing the best thing by starting out with the H100 engine instead. It's 100% bigger and will always be a better bet seeing as it's not a difficult engine swap from what I've read.

Any gains from tuning will be bigger IMO on the 100cc motor too. Sure I bet there were some tuned to the edge 65cc specials back in the day that went like stink, but if you can easily fit a large capacity motor that's making for an easy 65mph machine, it's a better bet than £££'s or far more on tuning the 50cc.

I think the H100 engine is based heavily on the MBX/MTX80 unit, lots of bits look almost the same.

For me I'd say a custom pipe designed for the 100cc engine would be a smart move and almost always the best bolt on power producer too, as would a careful re-build and light fettle. Can you get a V-force or similar reed block from a CR80 or similar engine that would fit the H100?

Honda road and MX bikes don't seem to have as much parts sharing or be based on each other as much as other Japanese makes are. But there's probably a slightly larger carb, and reed block from such a model that will fit or can be made to fit the H100 with a bit of work.

[flearider]

problem with 2 strokes is you have to watch them all the time finicky little things ..
had an rs125 yrs ago nippy little bugger until I put 2k miles(that put it over 10k) on it and was doing 90-100mph when the piston just gave out locked up and almost made me cack my pants ..it was a case of why is my back end bouncing like a ball ...clutch brake pull over smoke 3 fags omg it's dead ..had to push it home bout 10 miles
stripped down the head and thought wow that's really fooked and sold it ..

[Fladdem]

I was looking at all sorts of power mods and decided the best starting place would be the larger engine rather than fannying around with cheap ebay kits.

Got an MTX80 pipe, doesn't quite fit round the top of the 100 head, the flange needs cutting off, rotating about 10 degrees and welding back on. I have a H100 CDi unit, and some sort of clamp on air filter, which I need to come up with a solution to making fit inside the air box at some point, because sleeper.

I think I've got an NS125F reed block and intake. A carb off some sort of MX bike, an air cooled CR80, I think, I bought all of this four years ago and have never got round to do anything with it.

I've got the front end off an MTX 125 RWD that needs bodging re-engineering to fit. A jack up kit on the back, 30MM. I was going to get an early drum braked 18" CG125 wheel so I can get proper sized knobblies on the back, to go with the MTX 21" front. Is the H100 rear wheel an 18" or 17"?

I have seen the MB80 Athena 125 kit, and again wondered if it would fit the H100 bottom end, I would need to inspect both engines really, or just buy it and risk it.

I've provisionally sold the GPZ tonight, after about 18 months of knocking about in the garden and going down the road on it twice, it's going to the lad I bought the Mito off, ready to be butchered into a cafe racer. At least it should help pay for MonsTer5 funds.

Which reminds me, I have a Cagiva in the garden that needs sorting. Could tune that to a knifes edge.
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Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[Shaft]

[picture_man36]

If I knew then what I know now... I'd have sourced a set of standard barrels and put the TZR250 in deep sleep My £ 800 would have been £ 2500 today
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'The Picture Man'