DT125R ARCHIVE

FunkeyMunkeyDavid · Guru

RE: 1999 yz/dtr 170cc athena hybrid build

endurodt125 · DTR Respected Member

aha cool and Yer I was expecting to have all sorts of problems but nothing major so far ....even Thoe after a test ride on the weekend I've realised it is lacking bottom end and my exhaust has started blowing from the stub so back to the drawing board with the exhaust and I'm going to check the servo is set up right ..be back in a couple weeks with some more pics and updates ...waiting for payday is a killer I just want to get some more bling bling lol

Victor · Guru

endurodt125 wrote:
Yz engine no good for greenlaning ,you have to constantly rag the **** of them ....it started. Off me having a dt and loving it but seeing as I only used it for greenlaning I noticed the suspension, brakes and weight was not good so I decided to build this .....and yes I could of probably gone out and bought a ktm or something but where's the fun in that I enjoy building ...I've spent over 4k and intend to spend more just because I can and the feeling of knowing I built it is much better than just picking one out the shop

4k!!!!! gold piston or something? Joke, I salute your dedication sir!

endurodt125 · DTR Respected Member

Calum122 wrote:
That's pretty sweet.

The Athena it wasn't so much the porting, although it definitely could benefit from a bit, it's the fact that the barrel was modeled on a DT200R barrel. And as such it needs some material shaving off the top and then a spacer placed on the bottom. Just wants everything raised a few mm.

dude do you know anyone that's done this?

Calum122 · Guru

endurodt125 wrote:
Calum122 wrote:
That's pretty sweet.

The Athena it wasn't so much the porting, although it definitely could benefit from a bit, it's the fact that the barrel was modeled on a DT200R barrel. And as such it needs some material shaving off the top and then a spacer placed on the bottom. Just wants everything raised a few mm.
dude do you know anyone that's done this?

It was some chaps on the German forums that did all the measuring and worked out what needed to be done. I presume they went ahead and carried out the work.

endurodt125 · DTR Respected Member

Ahh I see ,I'm going to give it a go ...not very impressed with the kit and I managed to heat seize it :( so thought I might aswell do it while the barrels off for a replate

Calum122 · Guru

Yeah I'm not surprised mate. It was a hunk of junk when I had one a few years back. I think this chap here has done it:

www.nopitz.de/produkte/zylinderkits/yamaha-125-ccm/

I reckon he's done it to that '185' kit. That has to be an Athena kit with the correct work done to it.

-- Edited by Calum122 on Saturday 3rd of January 2015 04:33:58 PM

endurodt125 · DTR Respected Member

Ooohhh I thought the 185 was a myth lol hopefully going to get it all done over the next few months so I'll try post all the updates

Calum122 · Guru

Hhmm see I reckon it's the Athena 170 kit, relined with OS piston in it. And then ported to finish.

Sam M · DTR Respected Member

The 185cc kit off that site is a standard barrel using a huge liner Cal and a 68mm piston. He does sell a 200cc barrel using the standard barrel bored to 71mm with nikasil plating and.... he also sells a complete 200 engine (201cc) using a blaster/wr/dt crank 57mm with the athena top end with a 66mm piston from the looks of it. Been doing some research and want to try my own 185cc kit or there abouts if i can find a shop willing to do such a huge liner and if the owner of said website will divulgue some of his secrets to me pistons ect. If it is possible to slap a wr/baster crank into a dt it would be a good way to make a few more genuine 200cc dt using the athena top end which already has the correct port timing.

Calum122 · Guru

Sam M wrote:
The 185cc kit off that site is a standard barrel using a huge liner Cal and a 68mm piston. He does sell a 200cc barrel using the standard barrel bored to 71mm with nikasil plating and.... he also sells a complete 200 engine (201cc) using a blaster/wr/dt crank 57mm with the athena top end with a 66mm piston from the looks of it. Been doing some research and want to try my own 185cc kit or there abouts if i can find a shop willing to do such a huge liner and if the owner of said website will divulgue some of his secrets to me pistons ect. If it is possible to slap a wr/baster crank into a dt it would be a good way to make a few more genuine 200cc dt using the athena top end which already has the correct port timing.

See I don't think so. Nev had his Stock barrel BORED OUT TO MAX! 144cc. And this was bored so much that he had no choice but to pin the powervalve. I don't know the ins and outs of what Nev had done but that's the jist. So if nev struggled at 144cc then I can't imagine the cylinder walls even holding out at 185cc! There would be nothing left of the transfers.

Sam M · DTR Respected Member

Ah yes my bad on another good look it appears the 185cc kit doesnt look like a dtr barrel :( but the 165cc and the "Edition 200 gold"kit look like they use the dtr barrel although you can hardly tell looking at the tiny pictures. If you look on the underside picture of the "Edition 200 gold"kit it kind of looks like there is only a liner sticking out of the bottom and the alliminium skirt is gone alltogether....or am i completely wrong haha. I want his secrets :)

Theoretically could you not machine a hole 76mm through the barrel completely getting rid of the alli skirt which is 76mm which would inturn get rid of some of the inside transfer walls. Then press in a liner around 4mm thick in the barrel. The liner would now be the inside of the tranfer port walls(admittadly you would/should open the tranfer ports up on the outside), the internal diameter would be 68mm giving you a 185cc on standard bore. All theoretical and probably not possible but i like to day dream.

Calum122 · Guru

That 200 barrel wouldn't last 5 minutes. That wall is far too thin! it wouldn't handle the stresses from the heating and cooling let alone the explosion.

200cc on stock barrel would not be attainable. Even if you moved the walls further back you then reduce the transfer ports needed for the scavenging process and thereby would have a resultant loss in power.

endurodt125 · DTR Respected Member

I'm just going to mill 3mm of top of barrel and make a 3mm packer plate out of ally to get the port timings right then skim the head slightly for a tighter squish .....heard/read a lot of people are advancing the timing ...is this something worth doing?

endurodt125 · DTR Respected Member

Fmf fatty came today ...I swear I'm getting 1 step forward and 2 steps back with this build :/

Calum122 · Guru

Use a zeeltronic ignition system mate.

Get a specialist to work out the port timing mate. Can't stress this enough.

endurodt125 · DTR Respected Member

Could only find a zeeltronic for a five wire servo mines a 3? They look a bit too technical for me nd I was going by this with the port timings (the pic) also had a few people say the same

Calum122 · Guru

Yeah tjat's what I read. From Nev. he's a mod on here.

It's not complicated and it's the best thing you can spend your money on. Believe me I know I have one on my dt and it hands down beats any of single mod on my bike.

Sam M · DTR Respected Member

So are you still running your 170 kit cal? Did you get the spacer and machining done or just fit it with the ports out? I wonder how much better it will be with the port timing corrected having trouble finding any threads on the web where people have actually set them up right.

Calum122 · Guru

No. To be honest I never owned the 170 kit. But my brother had it on his and I had his bike for a while whilst I waited for my DT to come through. Don't mean to lie but just coudln't be bothered to explain.

The 170 Athena kit I experienced was on my brothers 2001 dtr with a 38mm carb and a few other subtle mods. No where near as extreme as my dt now. The torques out of it were okay, but it lost complete over rev and didn't perform as expected. I literally just turned 17 when I was using his dt and just came straight from my rs50, so of course at the time I thought it was quick but when I bought my dt I soon changed my perception about the 170 kit. And along with the other bikes I've ridden and other big bore kits and can now see on reflection that it was a piss poor bore kit.

Thats when I went on the researching missions as to why and how can I make it better. This is when I discovered big bores are not always the answer and sometimes you're better off with the screaming 125 barrel with appropriate mods...hence the 4DL project.

Sam M · DTR Respected Member

Ah i see. Dont you think the fact it lost over revs and performance wasnt as nice as it should have been is most likely down to the fact the ports are 3mm lower then there meant to be? I mean i dont think the standard barrel would perform to the revvy standard it normally does if the ports were covered by 3mm of the piston, thats got to absolutely ruin flow. And as you and other reviewers say they gain noticeable torque (even set incorrectly) so surely there is alot more gains to be had, because as we know lowering ports puts more of the power curve to the bottom end and raising them raises top end strength, so..... maybe the old Athena kit could be a singer yet? Food for thought. My top end failed a few days ago and i have decided its time to play, so the plan is to rebuild the bottom and top (hopefully with some changes to the top) im just finding the idea of spending £430 on a kit i will have to machine straight away abit silly but the more i think about it the more i want to do it.

Calum122 · Guru

That's exactly what I thought.

But even IF you correct the port timings you will always lose over rev on a big bore kit, sorry that's just the nature of bigger pistons. Hence why little citreon saxos rev so high.

ALSO the bigger cylinder WILL mean a loss in crankcase pressure and therefore airflow speed is reduced and this will affect a carburettor engine. And increase in wear on components due to the now imbalanced engine.

For general riding I think it'll be fine. But I still think there is more peak power to be had out of the 160 kit that the germans offer. That would be where I'd spend my money.

Sam M · DTR Respected Member

True your always going to loose some top but theres got to be more to be had with the kit being so poorly designed for the 125 engine, do you know of any threads or info from people that have corrected Athenas mistake anyone?. I am intrested in the german 160cc kit dont get me wrong. But once again has anyone seen any threads of people fitting any of those german kits? i cant find any reviews and it alot of money to spend on a kit with no real proven info. To be honest i have a yz125 to rev the nuts off :) so id prefer some more grunt on the dt and not have to rev the poor girl so hard (i have no servo, so pinned open)

Calum122 · Guru

Again if you want more grunt then get a servo fitted. That will improve it ten fold. The Zeeltronic ignition system, again I rave about it, gives the dt SO MUCH MORE mid range. Not much over rev feels about the same but the mid range improvement is surprisingly noticeable. Then fit carbon reeds. Then get a decent expansion chamber. And then jet and gear accordingly. That will get you much closer to the Athena kit without losing power anywhere in the range.

If you still want more power then send your cylinder head to Mick Abbey. The cylinder head is where most of the power comes from so £30 to have mick abbey correct the squish band is a well worth while investment. Then you could ask to have the cylinder ported for more midrange at £130 it's not cheap but still cheaper than an Athena kit.

The zeeltronic, the head, the barrel and a decent carb is still cheaper than one Athena kit. And out the box will have more power overall. The zeel is £130. Mick abbey to do the work cost me £170 and a 32mm flatslide costs around £60. Money to spare and better performance with greater reliability. It's a no brainer.

ringo67 · DTR Senior Member

what engine are you tuning ? is it a R .would a X or RE benefit from the same tune ?

Calum122 · Guru

ringo67 wrote:
what engine are you tuning ? is it a R .would a X or RE benefit from the same tune ?

All the same

Sam M · DTR Respected Member

"Again if you want more grunt then get a servo fitted. That will improve it ten fold. The Zeeltronic ignition system, again I rave about it, gives the dt SO MUCH MORE mid range. Not much over rev feels about the same but the mid range improvement is surprisingly noticeable. Then fit carbon reeds. Then get a decent expansion chamber. And then jet and gear accordingly. That will get you much closer to the Athena kit without losing power anywhere in the range."

I see what your saying Cal but this bit "That will get you much closer to the Athena kit without losing power anywhere in the range." how do you know how much gains the Athena really gives if youv never ridden one with corrected ports that is my question? Although you are right probly better to get a zeel. Another question my loom has been hacked when it was stolen and it doesn't have any wires coming out of the cdi for power valve servo. Would you easily be able to set up the zeel to run my powervalve or will I need a new loom or cdi?

Calum122 · Guru

I'd be VERY interested in riding a corrected Athena. But bigger is not always better. You're looking at around £600 for a new athena kit then the required modifications to it to get it how it should be.

For that price you could have loads more toys that will make more effective use of the DT's power.

So the Zeel will have its own wires coming out for the servo. So that shouldn't be a problem.

By all means if you're going to get the Athena corrected then go for it. It could make very good power. But I would still want to run a Zeel on it. Would probably be an absolute beast then!

Sam M · DTR Respected Member

Sweet looks like tonights reading is into zeels. Ringo67 I have a 1996 dtr. Well now im going to have a serious think. AH! so much money as you said for the Athena, but im a machinist engineer so the skimming and the spacer plate would be free for me. I know bigger isn't always better but hey ho if you don't try how will you know. Would be nice to have abit of a guide (with pics) for others to reference. Looking forward to hearing how yours goes when the works done endurodt125 have you sent it off yet?

endurodt125 · DTR Respected Member

Won't be till next month now as my daily commute needs a rebuild but I'm deffiantly doing it I'll keep you guys posted