Dt175 Cylinder On Aty175

[bestrcpilot]

As anyone tried a DT cylinder on a TY175? I have an early DT jug and I'm thinking of using it. I did find that the exhust port is 2mm higher in the DT then the stock TY cylinder. And that the intake port is 3mm wider as well. Also the DT cylinder head also has a smaller compression chamber in it, but will need the fins cut down to work.

[tony27]

Gaskets seem to be the same part numbers for ty175 & dt175 up to c model, only way to know for sure is to compare the cylinder heights from the base to the top for a start then see if it will fit cases.

Think I remember Feetupfun as having done something similar

[feetupfun]

The early series DT175 cylinder will fit to the TY175 bottom end (twinshock DT175 models ABCD sold in 1974/75/76/77)

78 model (E model - first monoshock - radial fin head - plastic flywheel cover) has different cylinder stud layout pattern so would need work to make it fit to a Ty175 bottom end

Yes I think you might need to trim the DT head fins to clear the TY175 exhaust pipe

The higher top edge for the exhaust port will reduce the low-RPM power compared with the TY175

The higher compression ratio will make it very slightly easier to stall at extreme low RPM

If you use a bigger carby than the TY175 carby you will get the full benefit of the exhaust port height difference

For a while I rode a TY175 with complete DT175 motor including the 26mm carby from the DT175, but with TY175 flywheel, and it was fine for trials riding, and magic for trail riding. It had a fair bit more power on top and the gears being equally spaced made for very easy trail riding. I didn't mind the slightly less bottom end power but only first gear was any use for trials. Second gear was like third on a TY175. The DT175 motor I used was the E model which looks a lot different externally, but appears to be very similar to a DT175A motor I also have, as far as compression ratio and porting goes.

The DT175E motor requires the TY175 frame to be dented in one spot under the motor for clearance, and the standard TY175 exhaust pipe is a very close fit without trimming fins at the front of the cylnder, or over the top of the head. The Ty175 flywheel needs to be trimmed a bit and the inside of the DT175 casing also needs trimming for there to be clearance

[bestrcpilot]

Thanks for the info guys. I think I'm going to try the DT cylinder a little more top end I would like and is what I'm looking for. Always want more power.

[feetupfun]

Here is what the TY175 with DT175E motor looked like

[ducman]

Put a DT 360 or DT 400 engine in and you have a rocketship :icon_salut:

[jc2]

With a DT A/B/C cylinder you need to alter the bottom fins & attach the TY175 clutch cable holder (or similar) to make the clutch operable. (On the DT175s, the cable holder was on top of the crankcase & part of it.)

[feetupfun]

Photo of DT175A motor to illustrate the mods mentioned by jc2

[feetupfun]

Put a DT 360 or DT 400 engine in and you have a rocketship :icon_salut:

but that would be a 100kg rocketship

[steve_earle]

I used to have a Whitehawk with a DT box, I think it may have had the TY head and barrel. It was a flying machine compared to the std TY 175.

[jc2]

I have been trying a DT175 cyl & head on my TY175. I have several to choose from, some with Exhaust 1.5-2mm higher than TY but others very close to same on Exh & Transfers. All stamped #443 & all with wider reedvalve. One head is stamped #559 & is off a C model which has higher C.R. & less squish clearance.

I tried a barrell with the porting closest to a TY, except that the rear boost port had been raised 1mm & re-angled with a fair bit of meat removed from the roof & angled towards the top of the reedvalve stops (if that makes sense). All in all it opens up the boost port quite a bit.

I chose the higher C.R. #559 head, raised the needle 1 notch & pilot jet one size (to 27.5 as John Cane had suggested in one of the mags) using the 22mm TY carb but with wider DT reedvalve and std Yam steel petals. Ign is std Yam points & timing was fairly advanced. Flywheel weight standard.The piston wasn't exactly fresh, but serviceable.

I ride old style without the clutch & apart from a slight 'fluffiness' & hesitation just off a very low idle, it was rather aggressive with noticeably more power almost everywhere it seemed & it revved to the moon & kept pulling strongly.

I then tried it with a #443 head with C.R. closer to the TY & the fluffiness & slight hesitation seems to have gone. I've not ridden it yet in any sections so I can't draw too many conclusions but it does seem rather promising. It feels considerably more responsive than a std TY. So far I love it with these mods tho it may not be so good in mud, but we have very little of that here.

Edited March 17, 2015 by jc2

[bestrcpilot]

Thanks for the reply JC2

I finally put the DT cylinder on and used the TY head. The TY head had already been turned down in order to rise the C.R. And reshaped the combustion chamber. I could not help getting the die grinder out and raising the exhust port 2mm and working on the transfer ports as well. The intake runner and intake port got about the same as yours. I to had to richen the 24mm Mikuni flat slide, by rising the needle one and going up one size on the pilot and main jet. The timing is set to the same as always with the points opening at .110 inches before top dead center.

All I can say is the engine is better then it has ever been. Pulls strong right off the bottom and revs to the moon and keeps right on pulling. I'm now able to pull 3rd gear on the big hills that I could not before get up in 3rd or 2nd. I was thinking about taking some height off the stock flywheel but now think I won't.

I am looking for an ign system that will advance the timing as the revs build, as I think with a little less advance at the bottom it will pull just a bit better down low and still rev and pull at the top when the ign advance

Edited March 17, 2015 by bestrcpilot

[bontempi]

@bestrcpilot

I think you should try the electronic ignition of the DT 175 MX(thats the name of the model here in germany). This engine looks similar to the DT 175E

engine in the picture from feetupfun.

I am running this ignition in a few of my TY from 175 up to 210 cc and i am very happy with it. The only problem is, it does not fit the ty crankshaft, you have to use the crankshaft of the DT 175mx ( or E?).

But it is worth a try!

I always wanted to have a motor like the DT 175MX with added Flywheelweight and a trials-Gearbox.

So that is another thing needed to be done: add some weight to the DT MX Flywheel!