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Post Info TOPIC: 1999 yz/dtr 170cc athena hybrid build


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RE: 1999 yz/dtr 170cc athena hybrid build
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Yeah please do man. Will be well interested in seeing how that pans out

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its food for thought. I always thought that the engines did vary on different models. like the restrictions. In my yoof back in the 80s the dt/lc you usually took the air box off and swapped it for a k and n and changed the tail pipe for a dep or if I remember gionelli ( probably spelt wrong ) then when the mk1 power valve came out with no servo it was turn and lock the power valve in open racing reeds k and n and exhaust and tail pipe and if you had the money a Stan Stevens port and tune job. I could never afford to do the tune so never found out how fast they went. Although when I had my first kmx 200 all that was changed on that was a dep tail pipe and a k and n air filter and that was a good runner and left the kmx 125s and dt's but never went up against a proper tuned one though. to me it does seem funny that you can buy a Athena 170 kit and the porting is wrong. You would think this would be sorted at the factory ? Also I have not really seen anything much about the German kits apart from something about a 160 kit that looked promising.

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isn't this the same deal as the 3bn cylinders? 

with the piston at bottom dead centre the piston used to cover 1/3 of the transfer ports?

i've always been shocked that the athena kits are naff,especially as even the 125 kits for yz,s are strong?

if it can be sorted it would be cool



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Really FunkeyMunkeyDavid :O that's surprising if true shame on you Yamaha haha


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Meadows


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That seems unlikely. I did have a 3BN cylinder, never fitted it though.

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Little update ...found a nice bit of 3mm ally for the packer plate/base gasket ,just waiting for a gasket set to come so I can use the base gasket as a template and then I'll start cuting/drilling and swearing ;)



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Gharris


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I still want to stress you do the research and make sure that this is what is needed. Simple modelling clay to mesh the bores with can confirm what is needed. Also Athena may have ported the barrel this for a reason. Just saying. I don't want to be held accountable for ruining £400 ' s worth of kit.

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I am still sceptical about it , how can I measure the port timing ? What do you mean mesh the bores? I know the old trick with modelling clay to check the squish but wouldn't really know where to start with the ports ....is it as easy as getting it to bdc and seeing how much the piston pretrudes over the exhaust port ?

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Gharris


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I would have just gummed modelling clay to the bore where the exhaust port sits and pressed it against the wall until it reached the top. Then measure the clay off the barrel.

But ideally you want the barrel off the bike and then have it measured. Verniers might work. When I said to do it I meant to have Mick Abbey or Stan Stephens or a profession do it. Have them properly measure the port timings, the angles and what not and get them to port it properly at the same time.

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Do you think I could just take the barrel to a professional and they could do it or will need the whole engine ? Ideally I need someone who's worked on a Athena before

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Gharris


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for my penny's worth .If in doubt use a professional . Have @ucked two bikes before. Doing it my self . I know you learn by your mistakes but only if you have the money to do so.... I think its bad if the 170 kits are coming from the factory with the ports not right . just seems daft. This was something I was considering my self but I think I will go down the get the head and barrel professionally tuned bigger carb and exhaust . Although I will try and find out about the German 160 kits does any one on here know about them ?.

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The Athena bore been discussed on many forums (as has a few of the yz144 kits which are believed to simply be a yz125 kit bored out with no real extra porting work done to it, read a really good article a while ago cant remember where. A company bought both examined, tested, then ported properly and tested again with much improvement) just shows that Athena don't neccasarily test there kits properly. The general over all opinion is they are modelled on the 57mm crank not the dts 50.7. Obviously check it before you do any machining and if your not compfortable doing it endurodt125 you could always sell you knackered bore on to someone else :P I emailed the german site a few times and they aren't open until Febuary and unsurprisingly haven't answered any of my questions about how they do any of the work..... ah well was worth a punt

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Sam M wrote:

The Athena bore been discussed on many forums (as has a few of the yz144 kits which are believed to simply be a yz125 kit bored out with no real extra porting work done to it, read a really good article a while ago cant remember where. A company bought both examined, tested, then ported properly and tested again with much improvement) just shows that Athena don't neccasarily test there kits properly. The general over all opinion is they are modelled on the 57mm crank not the dts 50.7. Obviously check it before you do any machining and if your not compfortable doing it endurodt125 you could always sell you knackered bore on to someone else :P I emailed the german site a few times and they aren't open until Febuary and unsurprisingly haven't answered any of my questions about how they do any of the work..... ah well was worth a punt


 This is true.

HOWEVER! READ GRAHAM BELLS BOOK! Factory porting is VERY good. In fact it's incredibly easy to ruin the porting work on factory racers. So actually the Athena 144 was all that was needed. And the reviews were very good.



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Iv been reading well/dipping into a few guides, bibles ect for a while now Cal don't worry :) The factory porting may be VERY good (I do enjoy your capitals for emphasis) but the FACT is that Athena are a huge mass producing organisation and if they were lazy enough not to optimise the porting on there yz144 kit from their yz125 kit (a much better engine all around compared to the dt and I imagine a much more sold item) then I would not be surprised if they haven't done that much r&d on the dt170 kit which is largely sold to people that have too much money aren't use to looking at porting ect and have little if any mechanical knowledge.
Lets also not forget they sold this kit for several years with o-ring heads knowing they were receiving complaints about leaking before they did a rework and scrapped the o-ring. Had the heads re-machined to accept a new insert (with the squish and spark thread in) that would clamp PROPERLY onto a more traditional head gasket :) It would not surprise me if they new the porting was off but cant justify a rework and spacer plate made for every bore when most of the people who have them aint even realised there wrong and largely give them positive reviews. Just my 2 cents

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Meadows


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No the point I was trying to make here, that I literally reread again, was this.

Yamaha, a massive (almost did the capital thing there) organisation, spent millions in R&D creating a fully fledged race bike. Athena are no where near as massive, they simply don't have the funds to redesign Yamaha's YZ barrel and there wouldn't be much more you could do to it in terms of porting. Those engines are nuts. So the next best thing was a replacement barrel with a larger bore. I don't think they were trying to do anything else.

Did you read that article about the Athena 144 kit that people were using. Interesting read.

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But again that's just speculation, I don't know.

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"Yamaha, a massive (almost did the capital thing there)" haha :) my mistake Cal thought you were saying Athena were the shizzle not Yamaha. Which article are you on about? The one im thinking of was done by a mag, tuned a yz125, then slapped 144 on tested it against standard, ported and tuned 144 kit, ran it full bore for awell over 100hrs closer 200hrs I think, with out it blowing up. think it failed due to stone getting caught in chain and smashing bottom end casing. There test was trying to prove you still can get a decent 125 tune the nuts out of it and smoke most modern 250f while keeping reliability. Great read.

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Meadows


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Yeah that was the article I read. Was a sweet read.

Graham Bells Two Stroke Performance Tuning is also, believe it or not, a page turner! Lmao I literally couldn't put it down.

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Went and got myself graham bells book and learnt quite a bit from it so far ....also mocked my fmf up ,just got to get it welded at the stub ....i wipped the head of the 170 and took a look at these port timings ,the piston does cover the ports slightly at bdc but it dosnt look as much as 3mm (havnt measured it yet ) so ive started making a 1.7mm spacer out of ally just for a template and to give me a rough idea hopefully finish it off in the worshop at work today ....some of the pics arnt great but your get the idea



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Gharris


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Nice mate. Very good books by him.

Aww I'm actually buzzing from this build. You could build an absolute weapon if you sort out thag barrel. So fair play to you.

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aha cheers dude ,im saving for a deposit on a flat at the moment so things might be a bit slow but i finished the packer plate template thingy so ill put that on and take some measurements on the weekend , im thinking i might just get some gasket paper the right thickness and just make my own gaskets instead of an ally plate and then once ive figured it all out and measured everything twice ill take it to a machinist to get the correct amount taken off the top ,going to get the head skimmed a bit too just to raise the compression slightly but probably wont do that till last ....ive still got to send the barrel off for a replate and get a piston yet i got throttel happy when i was suppose to be running it in/testing it and she had a minor heat sieze :( probably could still run it but id rather everything be 100% .....anyway ill try keep ya updated



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Gharris


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If you're looking to raise the compression then I'd advise running forged engine mate. It's expensive but it will be able yo handle the stresses involved. If you skimp out here IT WILL come back to bite you. Grab a forged con rod and forged piston.

That's my two pence. I've done the same. Gone all put ported and raised the compression and have made sure that bottom end is up for the task

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Ahh ive literally just fully rebuilt engine with a brand new crank ,mains and seals its only done about 4 hours and i dont think i would be able to get a forged piston for a athena?

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Gharris


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Ive fitted many a 170 Athena kit before, never on my own bike. They always ran good even on standard jetting but offered no great topend performance gains but the low down bottom end power was way better than the standard 125. That's just my 2pence worth.

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Yeah true...forgot. Sure it'll be fine

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Cool ,got the dtr exhaust manifold welded to the fmf so thats all done just got to spray the weld with some heat paint i also took a gamble and ordered some tzr 250 reedblock spacers and they fit perfect so i polished one up quick and im guna try it out on the weekend and seeing as the the bikes not going to be done for a few months im going to spray the rear shock because the paints starting to flake a bit and its the only thing letting it down (ocd).....ill put some more pics up of the progress on weekend



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Gharris


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Started to strip it down thought i would do a little before and after ...more pics coming soon



-- Edited by endurodt125 on Thursday 29th of January 2015 11:34:01 AM

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Gharris


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let us know how that spacer works out bud! 

keep thinking about a play with spacers in the near future biggrin



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Right first pic is without spacer second pic is with (pics arnt great) and i finished spraying the spring just got to let it dry and put it all back together and the tzr 250 reedblock spacer didnt quite work out :( so im making some out of old reedblocks



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Gharris


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Shocks done and the reedblock spacers just enough to clear boost port :) ...more on the 170 kit  coming soon lol 



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