250-500cc WR360 modification - Why? Because it’s fun!

At the start of the year I purchased a 2010 WR300 with very low mileage on the clock.
It was great fun with a pretty savage power hit which is just the way I like it!
I decided not to modify & try to keep it reliable…

Anyhow it grenaded two clutch activator rods & one activator lever within about 200km riding.
Then I had the carb needle in the 2nd leanest clip trying to sort out 100kph cruise & burnt the head while having a hard play racing mates on a super fun winding 6km long bore drain track.

Sooo the fix for the WR300’s issues was to purchase a 1995 WR360!
Seems great mechanically - just the plastics are in bad shape.

The CDI seemed a bit dodgy so I swapped in the 300’s unit & it starts nice & easy now.
Bike was loads of fun with instant power & row through the gears just as fast as you care to shift!
The previous owner had sent the suspension out to be professionally rebuilt & it is super plush.
The brakes have obviously been given proper love as they are sooo much better than the 300’s untouched brakes.

The exhaust was bent & squashing a coolant hose.
As a quick experiment I fitted up the 300’s expansion chamber.
It raised the power band onset & gave a distinct hard hit.
Lots of fun but it signed off early & went flatter than with the original pipe, so I took it off again.
I repaired the first bend out of the head on the original 360 expansion chamber with a piece I cut out of the emissions pipe that came with the 300. It probably made no difference to performance but the exhaust pipe is no longer squashing a radiator hose.

I rode it a few times with the original Delorto carb & it ran alright but I figured it could be better so I swapped in the 300’s TMX 38 Mikuni.
I had previously done the Jarvis mods. I changed the idle to 70 upped from 50, the pilot to 27.5 down from 45, & upped the main to 440 from 430. I also put the GAY needle into the 2nd richest position this time…
It runs much cleaner & revs out just a tad further.

The clutch had no more available cable adjustment & had to be pulled all the way into the hand grip to disengage so I pulled the cover for a look. I mixed & matched 300 clutch rod head with 360 rod & got the adjustment I needed.
I also lubricated the cable.
Now I can feather the clutch with my index finger & I feel like I’ve got some proper control again.

I’ve read up on the Wallybean intake mods & decided to take a look at the intake tract.
After removing the intake & reed block I decided to scrap the reed stuffer & install the 300’s intake boot.
It’s not a straight swap but easy enough to adapt on if you are prepared to be creative. Could definitely be done neater than I have currently done…
Of course the intake swap meant that I had to swap in the 300's airbox and its carb connecting duct thingy.
Anyhow - WOW - goes like a cut cat & revs out much higher & very cleanly.
It’s a real gorilla now! Big power everywhere!

I’ve got a couple of tuning tweaks left to try & then I’ll swap the motor into the WR300 chassis - well that’s the current plan…

Cheers,
Jason

So yesterday I spent some time & swapped the WR300 expansion chamber back on to the 360.
It did fit last time but the port angle in the head is different so it wasn’t particularly great.
I twisted the 300 pipe just a tad so that it fits cleanly into the head.
Neither the 300 nor the 360 muffler lines up properly with the mount holes on the subframe so I just wire tied the 300 muffler in place for the purpose of testing.

It completely TOTALLY changed the power delivery!
Last time I still had the original Dellorto carb & original unmodified intake boot with reed stuffer & I found the power hit hard but just fell on its face very early.

To recap - Now it has the WR300 CDI, expansion chamber, intake, Mikuni TMX 38, airbox & the reed stuffer is removed.

The 360 screams now!
It has a very hard power hit like the 300 & in my opinion revs out faster & just as high if not higher rpm than the 300.
I had SO much fun thrashing it around this afternoon!

The difference between the two pipes is huge - but - they are both heaps of fun to ride with!
The 360 pipe is on song right off idle & the engine feels incredibly strong. You can feel it signing off but still has plenty of over rev. It’s a riot to ride in this configuration.
The 300 pipe waits for a few more rpm before coming on with a crazy rush & the rpm zings straight to the moon. The adrenaline rush is addictive…

With either pipe it feels like it is on the rich side so I’ll carefully test a size smaller jet.
I will make an adapter to properly bolt up a muffler instead of tying it on with wire…

Cheers,
Jason

I know the feeling. Making improvements on these old bikes is where the fun is for me too at this time seeing as I can't ride much any longer. Glad to hear someone else having so much fun making modification on these older bikes.

Yes I recon I have equal fun modifying & riding!
Tinkering in the shed & trying out left field ideas is a passion of mine.
Up until recently it was just cars that I modified & hotted up but I’ve always enjoyed riding motorcycles & they have engines to hot up too!

Bitchin’