ESE's works engine tuner

[mantonakakis]

By the way, how are you going to machine teacup transfers?

Sounds like he will have the cylinder 3D printed?

[TZ350]

[andreas]

Mantonakakis

Yes I can see how rebuilding that crank is way fun ,ha. About that lost cylinder, look at some earlier posts. Reeds are bound to be small and the room for enlargement probably ain't great either, don't know really maybe yz80/60 is a good place to start looking. Hope the tuning goes well, and don't be concerned with the B-ports floors not aligning at bdc, is no big deal.

[TZ350]

One of the main restrictions will be the stock reeds, do you have the main dimensions of your RD250 reed block, or happen to know of bigger reeds to fit the 125?
Attachment 347777

The bolt pattern dimensions on the RD125 reed cage is essentially the same as the RD250 - 350 - 400 and RZ cages which are all much the same except the later RD and RZ cages have fiber reeds.



RD125 reed cage compared to a RD250/350/400 reed cage.

[wobbly]

Thanks everyone on the input . Seems to be too risky to have a big exhaust port sideways on , the ring will bulge outward in that direction, and even with the ring pin opposite I can see
problems.
All just to get rid of a header bend.
The other thing that interests me about this project is that when I review the other engines in opposition ie up to 35cc on unleaded petrol , they all seem to be way ,way off the pace in both technology
and Hp.
its very easy , technically , for this engine to make 15 Hp @ 17,000 rpm - whereas it seems that many are super happy with around 8Hp.
That is only 11.3Bar , 164 psi - bmep , very conservative in relation to many designs I have done.
And at 17,000 + rpm as that is only 17 M/s Mean Piston Speed - again super conservative , with safe compression and completely normal ignition/combustion parameters.

But as is the case in mini aero racing , the boaters seem all consummed with rpm , spinning them to 22,000 rpm even though the Hp peak is way back at 17,000.
Is this something to do with prop efficiency - or some effect I am completely missing here.

[mantonakakis]

Yeah, main issue I will face with bigger reeds is width limitation. I think the opening in the 125 cylinders is about 34mm, approximately 3mm wall thickness? Not too much room to add bigger reeds. Stock reeds are good for ~20hp according to EngMod (21mm effective diameter should be good for much more than 20hp, though? Or maybe Dat2T is converting the two reed blocks into a single effective diameter? In which case, 21mm = 20hp sounds about right).

Just did a short highway test - If I trust the speedo, about 55mph top speed with a very strong crosswind and a big loose jacket, somewhat disappointing. Seems to run out of steam by 9k, power drops off sharply after ~8500. Runs slightly faster in 4th gear than 5th. No EGT sensor, but cylinder head temp seems in the ballpark ~320F after a minute of idling following a long climb (more than 1mile at 8-12% gradient with 50% throttle or more in 3rd gear), jetting seems in the ballpark too. My cylinders are a little out of the roundness spec, but even so I was hoping for a little better with new rings and a fresh bottom end with the stock setup. I am at 6000ft above sea level, I'll run the sim at that altitude and see if it changes the torque peak. Biggest thing I notice is that the bike does not seem to rev out as high as the stock dyno would suggest... Power band start to hit, then it drops out too soon.

EDIT: Sim results at 6000ft vs stock dyno:

[andreas]

Yes, it is tricky, considering the unfortunate long cylinder studs are also an obstacle. But welding, using putty or just grind it a little will fit something larger. One of those reeds was able to send a moped to 70 mph, whatever power that is. Flat on the tank, I remember the rd doing ~77mph stock and ~87 mph with just pipes.

[husaberg]

Did your RD lose a cylinder??
My RD125 is running again as of yesterday, with freshly-rebuilt crank (new rods, big-end bearings and pins) and bottom end. I chose double the fun for my first attempt at a crankshaft rebuild... Time for a little tuning today, then starting work on porting and pipe plan. One of the main restrictions will be the stock reeds, do you have the main dimensions of your RD250 reed block, or happen to know of bigger reeds to fit the 125?
Attachment 347777

The Rd125 an the Rd200 twins have smaller reeds but the same bolt pattern. as the RD250/350/400 and many others
Not sure if the reed cavity area is big enough for Rd250 reeds without some welding, but MX100 DT100 AG100or similar might be about, in between size. Plus are the same bolt pattern.
if I wanted to tune a small twin maybe start with a 200. As it s bigger.

[lohring]

Thanks everyone on the input . Seems to be too risky to have a big exhaust port sideways on , the ring will bulge outward in that direction, and even with the ring pin opposite I can see
problems.
All just to get rid of a header bend.
The other thing that interests me about this project is that when I review the other engines in opposition ie up to 35cc on unleaded petrol , they all seem to be way ,way off the pace in both technology
and Hp.
its very easy , technically , for this engine to make 15 Hp @ 17,000 rpm - whereas it seems that many are super happy with around 8Hp.
That is only 11.3Bar , 164 psi - bmep , very conservative in relation to many designs I have done.
And at 17,000 + rpm as that is only 17 M/s Mean Piston Speed - again super conservative , with safe compression and completely normal ignition/combustion parameters.

But as is the case in mini aero racing , the boaters seem all consummed with rpm , spinning them to 22,000 rpm even though the Hp peak is way back at 17,000.
Is this something to do with prop efficiency - or some effect I am completely missing here.

We needed rpm because the available props had limited pitch. We got around this by cutting and re pitching the blades, but that is still limited. We were thinking about a two speed, gear up transmission, but Covid postponed the project.

I have a lot of data on the 35 cc engine we modified for straight line records a few years ago. The picture shows the stock engine with the stock pipe. Just shortening the pipe and header was good for a big power gain. We threw this away with a shorter pipe for more rpm. Water injection got back a lot of the low end which helped accelerate up to the speed trap. Below is the full article.

Lohring Miller

[mantonakakis]

The Rd125 an the Rd200 twins have smaller reeds but the same bolt pattern. as the RD250/350/400 and many others
Not sure if the reed cavity area is big enough for Rd250 reeds without some welding, but MX100 DT100 AG100or similar might be about, in between size. Plus are the same bolt pattern.
if I wanted to tune a small twin maybe start with a 200. As it s bigger.

Taking measurements off of my computer screen on eBay ads, it looks like older DT100/RX50/etc reeds should work without modification to the cylinder and provide a good upgrade - they should fill the reed cavity nicely without having to cut, and it seems like they have about 30% more flow area. I suppose I could cut out the bridge on each side to gain some extra flow area as well, and cut new carbon reeds.

Sim results on a slightly modified engine (wider exhaust port top width to 70% of bore, 190deg duration, 2-stage auto-generated "modern" pipe with 1.8 horn, 0.7 tailpipe, 3.5 center - just a first pass) aren't showing much improvement from bigger reeds alone. The bigger reeds with stiffer petals, however (0.15mm steel vs 0.25mm carbon, to get 1st resonance up to the middle of Dat2T's recommendation), gave 5-10% more power across the whole range, cool.

[F5 Dave]

Yeah, main issue I will face with bigger reeds is width limitation. I think the opening in the 125 cylinders is about 34mm, approximately 3mm wall thickness? Not too much room to add bigger reeds. Stock reeds are good for ~20hp according to EngMod (21mm effective diameter should be good for much more than 20hp, though? Or maybe Dat2T is converting the two reed blocks into a single effective diameter? In which case, 21mm = 20hp sounds about right).

Just did a short highway test - If I trust the speedo, about 55mph top speed with a very strong crosswind and a big loose jacket, somewhat disappointing. Seems to run out of steam by 9k, power drops off sharply after ~8500. Runs slightly faster in 4th gear than 5th. No EGT sensor, but cylinder head temp seems in the ballpark ~320F after a minute of idling following a long climb (more than 1mile at 8-12% gradient with 50% throttle or more in 3rd gear), jetting seems in the ballpark too. My cylinders are a little out of the roundness spec, but even so I was hoping for a little better with new rings and a fresh bottom end with the stock setup. I am at 6000ft above sea level, I'll run the sim at that altitude and see if it changes the torque peak. Biggest thing I notice is that the bike does not seem to rev out as high as the stock dyno would suggest... Power band start to hit, then it drops out too soon.

EDIT: Sim results at 6000ft vs stock dyno:

Perhaps some duct tape would help?

Either that or a smaller jacket.

[teriks]

Thanks everyone on the input . Seems to be too risky to have a big exhaust port sideways on , the ring will bulge outward in that direction, and even with the ring pin opposite I can see
problems.
All just to get rid of a header bend.
The other thing that interests me about this project is that when I review the other engines in opposition ie up to 35cc on unleaded petrol , they all seem to be way ,way off the pace in both technology
and Hp.
its very easy , technically , for this engine to make 15 Hp @ 17,000 rpm - whereas it seems that many are super happy with around 8Hp.
That is only 11.3Bar , 164 psi - bmep , very conservative in relation to many designs I have done.
And at 17,000 + rpm as that is only 17 M/s Mean Piston Speed - again super conservative , with safe compression and completely normal ignition/combustion parameters.

But as is the case in mini aero racing , the boaters seem all consummed with rpm , spinning them to 22,000 rpm even though the Hp peak is way back at 17,000.
Is this something to do with prop efficiency - or some effect I am completely missing here.

Nah, quite the opposite on the aero side, we want large diameter props for efficiency, but have to keep the tips away from M1.
Id say the lack of ignition system is why we have to shoot for rpm instead of crazy bmep, glow plug ignition is a mess.
We do run rear exhausts though, with ports up to 180deg width. Then again, we don't have to worry about a piston ring.

For some reason, our testing showed slightly lower power on rear exhaust engines over conventional side exhaust engines. We couldn't come up with a good reason and set records with both side and rear exhaust Quickdraw engines. If the engine has open transfers like the early RCMK engines, you will get very rapid piston wear.

Did all of the rear exhaust engines have those open transfers? If yes, wouldn't that excessive piston wear be a prime suspect for the missing power.
That issue wont be there on the new design, that just leaves any potential issues with the ring... depending on lohrings answer that is.
EDIT: Now that would be too obvious, surely lohring would have seen that connection if my interpretation were true...

[mantonakakis]

Perhaps some duct tape would help?

Either that or a smaller jacket.

I need a full streamliner!

[husaberg]

Taking measurements off of my computer screen on eBay ads, it looks like older DT100/RX50/etc reeds should work without modification to the cylinder and provide a good upgrade - they should fill the reed cavity nicely without having to cut, and it seems like they have about 30% more flow area. I suppose I could cut out the bridge on each side to gain some extra flow area as well, and cut new carbon reeds.

Sim results on a slightly modified engine (wider exhaust port top width to 70% of bore, 190deg duration, 2-stage auto-generated "modern" pipe with 1.8 horn, 0.7 tailpipe, 3.5 center - just a first pass) aren't showing much improvement from bigger reeds alone. The bigger reeds with stiffer petals, however (0.15mm steel vs 0.25mm carbon, to get 1st resonance up to the middle of Dat2T's recommendation), gave 5-10% more power across the whole range, cool.

we had a Ag100 which was the in between size I assumed the MX100/DT100 was the same looking at this it might not have been.
maybe earlier was smaller same as the AG100? while later one are bigger.
looking at the parts fiche the AG100 is likely the same size. as what you have.

edit looked the RD125 looks smaller
what I have found is one of the earlier CT2 which had the similar bolt on manifold which would give a straightish inlet
which looks te same size as the AG100 its made for a 22mm carb and I bet the stub is available cheap.
https://www.allensperformance.co.uk/...ormation-page/
okay found this also
https://yamaha-rd125.blogspot.com/20...a-rd125-a.html

https://www.cmsnl.com/yamaha-ag100h-.../#.X76jzGgzaUk


https://www.ebay.com/itm/Yamaha-RX12...e-345-13613-70.
Yamaha RX125 DT100 DT175 RT180 RD250 RD350 TY250 MX100 Reed Valve 345-13613-70
the reed dimension or the RD250/400 are well known and the late YZ85 is a single petal design from the factory and V force are available.


http://erlenbachracing.co/reedcages%20mods.htm

[lohring]

The side and rear exhaust engines we tested had either liners or standard closed transfers. Quickdraw once made crankcases for both types that differed only in the bolt pattern and cutout areas for the transfers. I have one of each type that are going into the proposed opposed piston engine. The ringless piston engines used in smaller models don't seem to have the same issues, but I'm not aware of anyone who has done careful test comparisons. Boaters use a variety if bent headers to run all types of exhausts. Below is the most extreme, a 180 degree header. I've run one of these engines and it was definitely more powerful than the older rear exhaust version. However, the one piece design of the new version was stiffer along with a bigger intake and other factors.

Lohring Miller