DT125R FORUM

@SpookDog Could always fit 2 calipers
https://www.50stunt.com/v/vspfiles/assets/images/yamaha wr250x dual caliper bracket 50stunt.jpg

https://www.50stunt.com/YAMAHA_WR250X_DUAL_CALIPER_HANDBRAKE_THIRD_BRAKE_p/smhb_wrx.htm

@Calum said in Seized rear suspension relay arm nut removal hack:

@SpookDog Pretty sure I just measured the ones that come out and ordered the same again off SimplyBearings.co.uk

@Calum do the same just measure then buy Koyo from Henderson Bearings on ebay. Use these for swinging arm https://www.ebay.co.uk/itm/274836296252?ssPageName=STRK%3AMEBIDX%3AIT&var=575083436083&_trksid=p2060353.m1438.l2649

@SpookDog Crazy your gasket problems as done loads of engines and every head gasket from cheap white ones in those cheapo full gasket sets to athena gaskets and never had a problem. On barrels always use blowtorch on studs and 40 years working on 2 stroke engines and never snapped a stud yet. Remove studs then piece of glass with 240 wet & dry on barrel and head and 100% flat, I use my cooker hob as it glass really strong and it
doesn,t move about, just do mine when the wife is out.lol

@StuKing94 Stay away from it as not a 2001 and
not even any 2001 parts on it. Should be like this genuine 2001.
https://pasteboard.co/xC8SKugS9JKs.jpg
https://pasteboard.co/iITMEcb8cfsb.jpg

@SpookDog Your previous barrel must of been worn out and lack
of power if think 3MB00P has more power as so mildly ported, the
P stamped parts had slighty more power as had different carbs etc. The P stamped head is standard 3MB head just without the casting numbers on top..

@SpookDog Hi, Everything there is to know about the TZR125 and every mod ever been done to Yamaha 125 engine on mates
website. http://www.tzr4dl.com/index.html.

@SpookDog Use "Silkolene Comp 2" .Left months in tank no jet issues. 32:1 so use 1ml of oil to 32ml of fuel (32ml oil to 1L fuel).
https://www.ebay.co.uk/itm/331841241723

@oisin Here a some pictures of the parts, have given you a set of Carbon Fibre Reeds for free. If you give me your email will send lots of high resolution photos of the parts as don't know how to add images here properly.
(https://hosting.photobucket.com/images/i/portingmaster/1.jpg?width=450&height=278&crop=fill)
https://hosting.photobucket.com/images/i/portingmaster/2.jpg?width=450&height=278&crop=fill)

@Oisin The cylinder has been rebored and honed with a quality
Namura piston kit, comes complete with modified powervalve and a brand new Japanese little end bearing. Has been re-painted in VHT met silver. £200 plus delivery
cheers Terry

@calum Will be getting it dynoed at Mick Abbeys in a couple of weeks so will upload dyno results and video of its power run once
sorted. cheers Terry

@Oisin Have a 3MB00 barrel with a 56.75mm Bore Namura Piston Kit just been bored & honed at Mick Abbey Tuning. still at Micks buf will be picking up this week, pm me if want it and will
upload some photos. cheers Terry

@arild Added boost ports and modified powervalve to suit, can
upload port maps to add boostports.

@DtxPower Best jetting for Athena 170 is 300 main jet on the
standard Mikuni tm28 carb but with the powerjet blocked off. Just cut the rubber tube in half from the float chamber to the powerjet then block the 2 halves of the rubber tube with a couple of 5mm threaded bolts or similar.

@waale2004 Best jetting for Athena 170 is 300 main jet on the
Mikuni tm28 but with the powerjet blocked off. Just cut the
rubber tube in half from the float chamber to the powerjet then block the 2 halves of the rubber tube with a couple of 5mm threaded bolts or similar.

The first people with a 170 kit lifted the cylinder 3mm, hence the terrible torque curve..but from then on the myth that the 170 kit needed 'port adjustment' was set in stone..while it benefits from porting, lifting the whole lot 3mm is a bad idea...The Athena 170 cylinder is the same casting as the 125 but bored out to 65mm. Most people reported a good increase in bottom end grunt but no real gain at peak hp. It turns out this is mainly due to the cylinder casting being the same as their 125cc cylinder, so has 125cc sized ports.
I opened them up to 170cc sized ports by widening the exhaust
5mm, and lifting the transfers 1mm using a 1mm base spacer
and 1mm skimmed of the top of cylinder. It is better raising the
cylinder rather than modify the transfer ports as the Nicasil
plating chips easily.

Double check the pv cable setting. On mine with the pulley
lined up with the mark, it was only about 3/4 open. Only when
I looked up the port did I spot why it felt so flat initially!
Initially the 170 kit felt awful, until I double checked the pv
setting and found it was about 3mm closed. Once that was
reset, it flew...

@lllDennis Best jetting for Athena 170 is 300 main jet on the
Mikuni tm28 but with the powerjet blocked off. Just cut the
rubber tube in half from the float chamber to the powerjet then block the 2 halves of the rubber tube with a couple of 5mm threaded bolts or similar.

@lllDennis Two-stroke piston seizures are either thermal-related or lubrication-failure-related. That one appears to me to be lubrication in nature. Could be overly rich jetting that allowed liquid fuel to wash oil off of the piston skirt as the fuel comes through the transfer ports, causing a lubrication failure.
If you need a gearbox have a couple of complete low mileage boxes can do you cheap.

@calum The first people with a 170 kit lifted the cylinder 3mm, hence the terrible torque curve..but from then on the myth that the 170 kit needed 'port adjustment' was set in stone...(while it benefits from porting, lifting the whole lot 3mm is a bad idea) The Athena 170 cylinder is exactly the same casting as the 125, but bored out more and the pv is spaced further away from the bore. double check the pv cable setting. On mine with the pulley lined up with the mark, it was only about 3/4 open. Only when I looked up the port did I spot why it felt so flat initially! Exhaust port width limit is 73% of the bore diameter with good rings (measured straight across). So 56mm bore is 41mm and the 65mm bore can be opened up to 47mm. Although in the interests of safety I've stuck with 45mm for now (70%), same as the standard RD350. Most people reported a good increase in bottom end grunt but no real gain at peak hp. It turns out this is mainly due to the cylinder casting being the same as their 125cc cylinder, so it has 125cc sized ports. I opened them up to 170cc sized ports by widening the exhaust 5mm, and lifting the transfers about 1mm.
Initially the 170 kit felt awful, until I double checked the pv setting and found the spool must have a different end for DT's, as even with the pulley lined up, it was about 3mm closed. Once that was reset, it flew... Mick Abbey said 30mm best carb
for ported 170 so fitted 30mm Koso-Pwk.

@arild said in Engine tuning/ bike build:

80 pounds to rebore the cylinder

£80 for a rebore is very expensive, Mick Abbey charges £25 for a
rebore and hone and postage abroad is only £10 as done a few
cylinders for overseas customers.

On my 2003 dt there a 3 grease nipples, 1 on swinging arm and 2
on the linkage bolts.