I'll take that as a no then

I did try to fit the 4JH airbox but there is no room for it,so i made an airbox using a 3jt box and cutting the top where the snorkle fits and replacing it with the 4JH snorkle,to let more air in ,i'v run the engine but not on the road so don't know how successfull it will be.

Do you mean no room under the tank, between the frame rails or both ?

Evilchicken0 wrote:I'd be inclined to touque it all before grinding the frame / engine.
If you do though you only need 2.5mm off each to equal 5mm plate ... can you get away with something thinner and therefore less grinding ???

Although the 2 plates are the same pattern technically they're handed

You can't really use thinner plate because you need something to thread into for the frame mounts. The adapter plates must be identical, countersunk or not, or the engine goes in twisted. For the sake of 10 or so minutes with a hacksaw to do the job properly, it's a no-brainer really.

The plates aren't handed of you take material off the engine too, but they are if you need to countersink them.

The method of torqueing everything up until it fits isn't right, it's wrong. Yamaha didn't design either the 3TJ/4DX or the 4JH/Thundercat around 'torqueing stuff until it fits' - the engines are a straight fit in their respective frames and building a hybrid shouldn't be any different.

I've had a batch of engine plates made up from 5mm mild steel if anyone wants a pair. They're identical and can be sent out threaded for either M10 x 1.25 or M10 x 1.50, countersunk or not- your choice- but they do require that you remove at least 5mm from the inside of the frame. They're £20 per pair, plus post.

hunter wrote:I did try to fit the 4JH airbox but there is no room for it,so i made an airbox using a 3jt box and cutting the top where the snorkle fits and replacing it with the 4JH snorkle,to let more air in ,i'v run the engine but not on the road so don't know how successfull it will be.

I tried cutting and shutting the 4JH airbox rubbers onto the 3TJ airbox but gave up and bought a couple of Ramair foam filters instead I'll make an ally or carbon plate up to fit under the tank to use the underside of the tank as the airbox 'lid' and see how that goes.

this is what i did,









To answer Evil's Question,they are too wide and too tall.

To answer Evil's Question,they are too wide and too tall.

Cool - cut and shut both ends, with the standard 3TJ (?) air filter

I think it's the only way to go,And air filter yep standard 4JH.

sorry i have read this thread but no one really cleary mentioned so i have to ask...

with the sprocket issue raised, can a thundercat (4TV) engine fit in a 3TJ frame and have the sprockets line up correctly as it would with a 4JH (FZR400) engine?

slowsport wrote:sorry i have read this thread but no one really cleary mentioned so i have to ask...

with the sprocket issue raised, can a thundercat (4TV) engine fit in a 3TJ frame and have the sprockets line up correctly as it would with a 4JH (FZR400) engine?

The 4TV and 4JH engines should have the sprockets at the same point- they use the same rear wheel, spacers and cush drive so there's nothing there that would point to a different arrangement at the front sprocket.

The issues that may have arisen with 4TV engines may have been down to how the engines were mounted in the frames- using the original method that puts the engine in twisted would give a slight offset from standard. Using the rear mounts to line things up then fitting the front keeps things all square.

If someone wants to give me 4TV engine to try in my bike, I'm more than happy to help!