Another Track Day

I did 2 x 20 minute sessions on the bike at Hampton Downs on Wed. March 20th.
The bike ran well and the 41 tooth rear sprocket was perfect in terms of just reaching 12,000 rpm at the end of the main straight. Very enjoyable!
Paul seemed to think that the bike didn't sound all that crisp anymore.
I was clocked at 1 min 22.4 seconds for a lap.

I did 1 x 20 minute session on the blue fairing NSR250 that is shown in some of the pics on this blog.
It is an MC21 engine in an R2j frame running PGM-1 ignition. (no battery required).
I was pleased to be able to notice that my bike was noticeably quicker than the blue bike.

I want to pull the heads and barrels of my NSR and maybe give the barrels a very light hone and fit new rings.
I also want to get the thing on a dyno, and get a horsepower reading.
This will have to wait though as I have other priorities.
Am heading into winter now, so,..   may go into hibernation for 6 months.

A look up the exhaust ports

I took the pipes off to have a look up the exhaust ports.
OK, well this doesn't look the best.
I did have a few high speed "clutch in" moments during the first 300kms.

I am fairly sure that this was due to the petrol tank breather not working properly.
This meant that a slight vacuum built up in the tank and hence petrol flow into the float bowls may have slowed down to a dribble or less and resulted in a lean condition after a while at high revs and max throttle.

I fixed this problem before my first track day and it seems to be running pretty good now at prolonged high revs/throttle.

Sadly it seems that the LH Cylinder in particular may have come quite close to seizing at some stage?
I am hoping that it will survive the next track day. Then I will pull the heads off and check this out properly.
Looks like I will probably be taking the barrels off as well.
Bloody fuel tank breather!!! Argh.

RH Cyl

LH Cyl

RH Piston

LH Piston

Scorchers

41 tooth Rear Sprocket

In order to get the gearing right for Hampton Downs racetrack, it seems that gearing of 15 tooth front, 41 tooth rear is going to be about right.

I ordered a couple of 41 tooth rear sprockets from TYGA Performance.
Including freight they cost NZ$179 or approx NZ$90 each.
I ordered them on Friday and they were at my door 8:30am Tuesday, from Thailand.

The TYGA 41 tooth rear sprocket weighs 293 grams Made from a type of aluminuim called Duralium? and anodised for hardness.
The standard Honda 42 tooth rear sprocket weighs 830 grams.
So, a nice way to save half a kilo.

When I went to fit the sprocket I found that my 110 link chain was too long and I had to shorten it to 108 links.

110 links works for 15/42,.. just. If things wear/stretch a bit, there is little or no adjustment left at all.
110 also works for 16/42.

Link Plates, Gear Shaft Extender, Radiator Bracket

Today I fitted the "compromise" rear shock Link Plates. (see previous post)

I also fitted a proper gear shaft extender so that the gear change mechanism no longer rubs on the frame.

I also fitted the little bracket that bolts on to the bottom head and holds the bottom pin of the radiator.

"Compromise" rear suspension link plates fitted 01

"Compromise" rear suspension link plates fitted 02

 I plan to do another track day in approx 10 days so it will be interesting to see if I notice much difference.

Rear Suspension Link Plates. Part 3

Yesterday, a couple of friends and I played around fitting different link plates to an MC18 R2j.

We compared the link plates by measuring the distance from the centre of the rear axle to the centre of the bolt that holds the rear fairing on just behind the riders seat.
18 " rear wheel.
Bike standing under its own weight.

The standard link plate measured 478mm
The standard link plate turned to have the "F-->" pointing up measured 488mm
The Compromise plate measured 504mm
The HRC plate measured 521mm

So very basically:
The HRC plates raise the ride height by about 43mm
The compromise plates raise ride height by about 26mm

The HRC plate makes the bike "look" way better in my opinion. However, the rising rate becomes pretty stiff pretty quickly. Great for the track, but perhaps a bit much for the road?

The compromise plate probably actually is quite a good compromise for road riders that want to do the odd track day. But it is very simple to change this part anyway.

See previous posts:
1) http://edetuckracing.blogspot.co.nz/2011/11/rear-shock-link-plate-options.html
2) http://edetuckracing.blogspot.co.nz/2012/11/rear-suspension-link-plates.html

MC18 R2j with HRC link plates (521mm) on right.

I recently put the "compromise" plates on the R6k and the distance from rear axle centre to rear fairing mount measured 521-2mm. About the same as the R2j with the HRC link plates.
I guess the subframe/geometry differs slightly from R2/4j to R5/6k.