buying advice (tz yamaha related)

[Mellorp]

Most people will disagree but if you own a TZ you need to know how to set it up. It's a different animal to anything else. IMO setting a TZ up on a flat surface with the only throttle action being wide open probably coincides with 10% of the time you ride it. Add in the weather, bumps, corners, extreme lean angles & braking (and wrong gearing) that all cause lots of wierd things to happen to throttle opening & response. You need to set these things up to how your ride, where you are riding and the conditions on the day, not how someone else would drag race it. OK the dyno will give you a base setting but from that point onwards you need to know how all the subtle changes to jetting and if you are lucky a programmable ECU, can make such a difference.  Losing or gaining 10% when you only have 70~75bhp to start with makes the world of difference. A cloudy cool day can make it fly and be on the point of seizing, but on the same jetting on a warm sunny day it will run like a dog and foul plugs. 
Some ancient old video of Joey Dunlop showed them riding round country lanes on their TZ's to set up the jetting. These days you have to use an open pit lane track day (unless you live in Ireland). Once you know how to jet them it's something you can do by feel when riding and just listening to the engine
However it's not my bike, my money or my time, just my opinion. 

[mattyam]

50 minutes ago, Mellorp said:

Most people will disagree but if you own a TZ you need to know how to set it up. It's a different animal to anything else. IMO setting a TZ up on a flat surface with the only throttle action being wide open probably coincides with 10% of the time you ride it. Add in the weather, bumps, corners, extreme lean angles & braking (and wrong gearing) that all cause lots of wierd things to happen to throttle opening & response. You need to set these things up to how your ride, where you are riding and the conditions on the day, not how someone else would drag race it. OK the dyno will give you a base setting but from that point onwards you need to know how all the subtle changes to jetting and if you are lucky a programmable ECU, can make such a difference.  Losing or gaining 10% when you only have 70~75bhp to start with makes the world of difference. A cloudy cool day can make it fly and be on the point of seizing, but on the same jetting on a warm sunny day it will run like a dog and foul plugs. 
Some ancient old video of Joey Dunlop showed them riding round country lanes on their TZ's to set up the jetting. These days you have to use an open pit lane track day (unless you live in Ireland). Once you know how to jet them it's something you can do by feel when riding and just listening to the engine
However it's not my bike, my money or my time, just my opinion. 

cheers  mate, i understand it will be a learning curve. i recall seeing the video of  joey in his flares flying up a  country lane on an old 350

[Jenny Pryde]

A friend who raced TZs used to record  barometric pressures and ambient temperatures and keep detailed notes on how the bike ran. That's before all the soothsayer stuff, 'reading' piston crowns and skirts.

Part science, part art, part magick.

[mattyam]

i think maintaining, and part understanding a thoroughbred 250 to do some parades/trackdays ect is a bit of a novelty in itself these days and definitly requires l knowledge and a decent idea of how a two stroke works . but for those that raced them aswell as setting them up to perfection were real throwbacks. using weather measuring equipment/det counters and exhaust gas temprature  to depend wether your bike will be capable of running at its optimun, go backwards or seize is amazing in itself.  i know a few that just run exotic grand prix bikes in parades and such and just have them on the safe side for the sake of the last few ponies. purely because there not racing them and parts availibility means they cant afford to have a mishap.  its a shame thats the parts availibilty and the end of pure race bike classes has come to this but i blame honda. and greta thumbblister. 

[lesviffer 750]

36 minutes ago, mattyam said:

i think maintaining, and part understanding a thoroughbred 250 to do some parades/trackdays ect is a bit of a novelty in itself these days and definitly requires l knowledge and a decent idea of how a two stroke works . but for those that raced them aswell as setting them up to perfection were real throwbacks. using weather measuring equipment/det counters and exhaust gas temprature  to depend wether your bike will be capable of running at its optimun, go backwards or seize is amazing in itself.  i know a few that just run exotic grand prix bikes in parades and such and just have them on the safe side for the sake of the last few ponies. purely because there not racing them and parts availibility means they cant afford to have a mishap.  its a shame thats the parts availibilty and the end of pure race bike classes has come to this but i blame honda. and greta thumbblister. 

This ^^^^, i have been involved in both racing 2 strokes, and thrashing em on trackdays, and believe me, there is a difference, when racing them, ( admittedly 20 years ago ) we were using barometers, weather stations and calculation factors, but in recent years i was parading and trackdaying a RS250 and  jetting it a little on the safe side with no adverse effects, also, my lad who raced 2 strokes in the 90's, took it out every year at the festival of 1000 bikes and it ran ideally. Another thing to remember is, maintenance schedules, if your'e not racing it, you wont need to replace as per the manual, as your not looking for that last inch to beat your competitor in the next race, when we were racing we would sometimes replace top ends halfway through a race weekend, but certainly not necessary parading or the occasional trackday. I think a lot of parading / trackday owners of these gp machines get carried away, when their not using it for what it was designed for. If you look at the Honda rs250 nf5 in particular, that engine was based around the road going nsr250, which certainly did not need rings every 300 miles and cranks every 1000, even if being abused. so if you got your gp 250 for nostalgia and a gentle poodle, use good quality 2 stroke oil, jet safely, keep an eye on it and enjoy.

 

 

 

,

[Ray Von]

Has it hi sided you yet? 

[bogman]

Mine has

[Mr Tea]

10 minutes ago, bogman said:

Mine has

Yea, but oil made you do it so you’re excused 

 

 

[dab33]

Be careful regarding mileage limits on engine parts. I know someone who ran his pistons to 400 miles and he literally paid the price.

Yes he was club racing it but not at the front.

I used to do a complete top end change every two meetings, which worked out at about 240 miles depending on how much of the test day I did.

 

[Mr Tea]

1 hour ago, dab33 said:

Be careful regarding mileage limits on engine parts. I know someone who ran his pistons to 400 miles and he literally paid the price.

Yes he was club racing it but not at the front.

I used to do a complete top end change every two meetings, which worked out at about 240 miles depending on how much of the test day I did.

 

Am I allowed to add that you rode dog slow doing those 240 miles ?

😙

[dab33]

On 4/23/2024 at 10:17 PM, Mr Tea said:

Am I allowed to add that you rode dog slow doing those 240 miles ?

😙

Yes as its probably true.☹️