I used a stock rod in my TS125/100. At the time I was using the TS, Suzuki had superseded most of the early TS rods with the later RM rods. The 125 & 100 were the same stroke as I recall. I balanced the crank with a slug of aluminium in each big hole. The original aircooled motor was 200 degrees on exhaust and piston ports and around 132 degrees on the transfers but they were much better angled than stock. That motor made a huge fat 19.9hp, see dyno chart purple trace, and lasted well, apart from the pistons which I replaced every 2nd meeting. I was using RG400 rear pistons if I recall correctly with just the top ring. TS125ER gearboxes are better than others but still not great. Clutches, despite being garbage, work OK with just screwing the springs in a bit. On my bike anyway. Use C3 clearance main bearings on the crank and plastic cage bearings if you can get them.
In the end I went full crankcase reed valve with a sleeved down RGV250 watercooled cylinder. Quite disappointing, but fun to build.
I enjoyed having a ride on that bike down south. Nice easy bike to ride . Which you keeped it . Saw the engine for sale in Steve green's mag for like 200 bucks . To cheap
i'm over buckets
Yes, I cut my teeth on Bells 2 stroke performance tuning book. But it has a serious flaw about maybe one of the most important aspects of 2T tuning. If it mentions it at all, it does not go into "blow down time area" in any detail.
"blow down time area" is the amount of area of the exhaust port uncovered before the transfers open and the time it takes to uncover that amount of exhaust port real estate at any RPM (time). So "blow down time area" is RPM dependent and gets smaller as the RPM increases.
Pretty soon "blow down time area" is to small to allow all the combustion gases to blow down in the time available. All things being equal, available "blow down time area" is the single limiting factor on 2T power and RPM.
"specific time area" is another modern concept not touched on in the book. "specific time area" is the "specific" "time/area" a port needs to do its job at any specific RPM/Power. So you chose your target power and the rpm to achieve it and from that you get your "specific time area".
After that it is a reality check to see if you can mechanically spin the engine fast enough and cut ports big enough to match. And in the case of the transfer/exhaust port balance if you can achieve the "blow down time area" required there. It is all a juggling act. Bells 2 stroke performance tuning book is a very through piece of work for its time and gave a useful guiding range of port timings but not much about the all important "blow down time area".
For my own projects I cheat a bit and use EngMod2T for working all this out.
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When a 2T has been run for extended periods at high RPM and the "blow down time area" has become insufficient you will see carbon buildup and staining in the transfer ports. Running out of "blow down time area" is the reason you can hold a 2T's throttle wide open and the engine RPM will build up then plateau.
Speedpro told me about a time he held the throttle wide open and when the engine rpm reached the plateau he could look down the carb and see flames dancing around in the crankcase.
Funny you mention that, yesterday I had read up to the expansion chambers section in the book took a breather had a play on YouTube and somebody mentioned the blow down time and I thought????? So i googled it and it's pretty much a key ingredient, as the nelson Kart track is quite small I will probably do some bits different i dont need all out top horsepower as it wouldn't be used very often, looking forward to getting a degree wheel, an the bottom end back together. I have been looking at small 90 degree die grinders around 80ish$ on aliexpress
https://m.aliexpress.com/item/328368...BoCT5kQAvD_BwE
Might be good for the small transfers ?
Do not touch the transfers.
Lift them to where you want them to be but it is far easier to mess things up than improve them.
Don't you look at my accountant.
He's the only one I've got.
Well, i must say.. i have been sorting though parts lists for hours and have come back to the TS185 rod multiple times it seems like the best choice as it comes with the right size B.E pin, it is 10mm longer but i can put a spacer under the cylinder and adjust the ports right? you found that almost instantly and it took me days i also looked at the RGV rods, YZ125 01 - 04, and the KX 125 03 - 08
Ø Small End (A) Ø Big End (B) Center to Center (C) Width Small End (D) Width Big End (E) Total Length (F) Eye to Eye Center (G) Ø Big End Pin (H) Length Big End Pin (I) Washers Remarks
ProX Con.Rod Kit TS125ER’81 A18.00 B25.00 C100.00 D18.00 E16.00 F129.60 G78.50 H19.00 I56.00 19 x 34.5 x 1.0
ProX Con.Rod Kit RGV250 20.00 28.00 105.00 16.40 16.40 136.70 81.00 22.00 47.00 None
ProX Con.Rod Kit YZ125 ’01-04 19.00 29.00 105.00 16.00 17.00 138.00 81.00 22.00 54.50 22 x 37 x 1.0
ProX Con.Rod Kit KX125 ’03-08 19.00 29.00 104.00 17.00 17.00 137.00 80.00 22.00 55.00 22 x 42 x 1.0 Barreled Rod
ProX Con.Rod Kit TS185 21.00 28.00 110.00 17.00 17.00 143.00 85.50 22.00 56.00 22 x 39 x 1.0
i would go with the TKRJ or Pro X but swap out the big end bearing for a flat cadge silver plated, plus silver plated washers buy a couple for spares at the same time.
there are other rods in 104mm length that will also work, but longer likely gives you more room for a decent inlet.
Just find the piston you want and work backwards to get the rod that suits.
But shit its your money just get a hooker........and a 2m ruler......plus 500mls of hand sanitiser
Kinky is using a feather. Perverted is using the whole chicken
Yes, being able to adjust the cylinder height to get the best possible port timing is the way to go.
Maching the top of the cylinder and or using a longer rod with spacers under the cylinder is a common way to get the port timing in the right place.
If you are cunning and imaginative you can also make the spacer act as an extra cooling fin.
Cool, that is good. i did read ya thread about the measures you took to cool that motor. very interesting experiment very out of the box but hey, if it works it works right?
now to do the same thing with a piston.... urggghh
Honestly, i have no clue what that pipe is coming from the auto oiler???!? i meant to ask about it but forgot. looks like a cool little motor.
I think that is one of Scott's old motors. The auto oilier has been replaced with a home made water pump. The engine had a sleeved RGV cylinder on it for 100cc.
Team ESE have used a lot of Kawasaki KX125 (56mm) pistons early 80's I think. Purchased of eBay. They are a dished top and Weisco ones come in over sizes. We will have used domed ones too. I will look in the shed tomorrow and see if there are any packets with details I can photograph for you.
With a dished piston and the head heavily skimmed back we got a compact combustion chamber with the plug electrodes pretty much in the center of it.
There are drawbacks with dished pistons, but you work with what you have got.
Ah, cool. i was going to run the bike as it was "stock" for abit to get a feel for how it all works and slowly chip away at learning how to tune a 2 stroke engine as things needed work, but after this lockdown and being bored, i thought meh lets check the top end out " due to it being difficult to start" ... i jumped down the rabbit hole head first. so i am looking to build a decent bottom end as a solid building block and try different combos in the top half as time goes by.
anything to get me in the ballpark will be great. i do want to get rid of the offset plug and o-ring the head but only because i am in this far already. i take it the only real way to do that is weld the head up and re-shape it ? any other heads that bolt on?
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