Cases
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To get DT to pull a lot harder should of fitted Athena 170 kit rather than a ported 125 barrel, have got a ported head and barrel off Mick and the 170 is miles better with the extra torque and being 20 stone the torque makes so much difference. My 170 is fully ported and revs to over 11,000 on a 2003 DT R using standard TM 28 carb with the powerjet blocked and standard air filter with snorkel on.
People who say ports are 3mm to low don't know anything about tuning as when mapped the ports and they are 125 ports and same hieght as 125 ports. The reason they don't rev past around 8,000 or so is because of the exhaust port width as on 2 strokes exhaust port width has to be a certain percent of the bore diameter, so going from 56mm bore to 65mm bore totaly screws up the engine. Exhaust port width limit is 73% of the bore diameter (measured straight across). So 56mm bore is 41mm and the 65mm bore can be opened up to 47mm.
Double check the pv cable setting on Athena kit as with holes lined up standard the powervalve is only 3/4 open, on mine set powervalve in cylinder flush then drilled a new 4mm hole in center of powervalve pully.
Engine tuning is all about everything working together and a combination of ports, compression, carb, ignition all perfectly matched. With the Athena kit most people run wrong plugs to suit it best like br9es or a br9eix irridium plug. The plugs to use on any ported DT are NGK B10EG non resister plugs along with 7mm HT lead copper core and a non resister plug cap.
The bottom end makes cruising more relaxed, and the extra top end means it'll now do a wheelie in 4th gear easy. -
@2stroketerry thanks for this, I'm half the weight so we'll see. It's all a bit of fun and it sounds like the 170cc kit needs porting to get the best from it. If I do go for bigger ccm I'll prob go 150cc as it Seems a good half way and used the std barrel.
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@Bluestoesonnose Two strokes also don't like over square engines. More power can be gained from the original 125 barrel I'm certain. I've had 170 kit in the past and it is a blast for sure. It was also a damn sight reliable, I just feel it takes a certain part of fun out of the 125, with the loss of overrev. But to be quite honest, that's not a bad thing.
There are many variations you can play with on these engines, I've yet to see a properly tuned up 4FU barrel on the DTR engine. I fettled with the concept on paper, but bottled it and sold my 4FU spares.
The stock porting on the 4FU looks better than the 3MB.
Also also, if you really want a decent 125 setup, then you will want the SP barrel. It will be comparable to the Rotax Gilardoni barrels, and they are superb!
Oh that makes sense, it's designed by Gilardoni. Yeah, that does make sense now.
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Can't see this reply properly as it comes up blurry.
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I'm confused by all the codes, remember I'm only learning about these engines atm
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@Bluestoesonnose The images? Yeah it's hosted through Flicker, or from Google.
But if you google.
Yamaha TZR 125 RR Belgarda SP Barrel
You should see exactly what I'm talking about. I've spoken to people who've ridden the SP engine and they say it's sublime.
Personally, it's no better than a Rotax 122 engine && Costs substantially more.
So just transplant a Rotax engine, or get a better bike.
The 4FU, again costly, is a more viable options.
in the end, I just spent a little money on the 3MBP barrel, but wasn't impressed with the results against a STOCK RS.
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So these things are a direct swap on the DT cases
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@Bluestoesonnose That's why I've linked you a video. The 4FU can be found on the European 4GW Belgarda TDR models.
Google and Search should help you find what you're after.
Yes they're direct swap.
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No idea what Rotax motor your on about though
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@Bluestoesonnose Rotax 122 barrel. £20
https://www.ebay.co.uk/itm/Aprilia-RS125-Mitaka-Barrel-1991-2011-Rotax-122-And-123-RS-125-Spares-Or-Repair/192690108309?hash=item2cdd39b795:g:0UMAAOSwaIJbdEd3:rk:7:pf:0And the difference between that, and an SP barrel is negligible, yet you'll pay £500 with an SP barrel.
Yes that one is the 4FU, but you will need the 4FU powervalve to suit.
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Hi @Bluestoesonnose I have a spare 4FU00 barrel with the powervalve if you want will post some photos, just make an offer as no use to me as Athena 170 kit on my DT
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I could be interested as I've just discovered that my spare barrel is FUBAR as it's got a crack in it
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Hi, photos of the 4FU barrel with powervalve fitted, you can see the bore is scored
so will need replating or reboring. Just make me an offer if any good to you.
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Hi,
Looks good to me, no idea what the going rate is for one, ummm £75 posted?
