DT125R ARCHIVE

Information On Yamaha's TZR125R 4HW 4FU00 Barrel

I want to collate information about the collection of cylidners available to us users of the DTR. I think it would be handy to have a library of different barrels with information so that people can effectively research information about different barrels. I'm looking for as much input as possible and will just add it to this one page (and of course add your name to the content creator list).

Was wondering whether or not I could get some input as to the benefits of this barrel. Drawbacks and whether these barrels are worth their value. Or maybe it's just the rarity of the barrel that causes it to be worth so much. I sort of want this to be a definitive answer to questions around this barrel. Hopefully to be used as some sort of guide for future users.

Barrel in question:

4FU on the right.

Look how much this side of the powervalve is recessed:

This is the corresponding powervalve endcap. It digs into the powervalve much more:

4FU Powervalve:

So what I know so far

• The barrel is found on the European spec Yamaha TZR125R models.
• The barrel will fit models:

• Yamaha DT125R 1989-2007 (Any model that will take a 3MB00 Barrel)
• Yamaha TZR125R 1993-?
• Yamaha TDR ?-?

• The barrel is Nikasil plated so there is no lining. Benefits of a Nikasil plated barrel I'm told is that they have better heat dissapation.

• Well actually I spoke to a Yamaha technician and he said the way in which Yamaha fuses their liners there is not much in it. 
• However it's worth mentioning that Motorcross bikes run Nikasil barrels.
• Also my brothers Aprilia RS125 Polini kit has a Nikasil liner.
• Also worth noting that the Yamaha TZR RR SP barrel is Nikasil plated (correct me if i'm wrong).
• So surely this just reinforces the bonus of running Nikasil liners.

• I've also been told that Nikasil liners are great...for race bikes where you change jets as a matter of course of action and that for everyday road use, just don't bother.
•  The Powervalve on these are completely different to the 3MB00

• They're stubbied at one side
• They have a massive indent where the powervalve cover slots into it
• The powervalve bush is different to the 3MB00 it's a tiny bit thinner

• I've been told that the 4FU has different port dimension to the 3MB and that the 3MB port dimensions are just bettter.

• The piston are flat tops (same as the aprilia).
• Thus flat tops run lower compression than domed pistons.

• How much is this true? Could you stick a domed piston in it?

• What would the draw backs here be?
• What benefits are there to be gained?

• Obviously cannot rebore these barrels.

• Or can you?
• Could you rebore it then plate it up and use a bigger piston.
• Effectively increasing cc's.

• Where else can these barrels be found?

• I thought I've read TDR belgarda or something...

I paid £60 for the barrel scored. £40 for powervalve end caps. £60 for a Powervalve. Still needs £140 spent replating it. A piston and its matching head for it to be complete. This is sort of a project for me. I will try and get it all complete, even if I never use it.