The seller here claims these came off an 1988:

https://auctions.yahoo.co.jp/jp/auction/q1132878077

For those who may not be able to access the Yahoo! link, or if/when it expires, here are some of the images:







Really interesting. As you've already mentioned, the OEM Parts List doesn't show an alternative backplate (it does however, show different pulleys):



This image is from Release 9 (the final release) of the '87-'89 Parts List, dated 10th March 1992.

Really weird! Every other model has the knock-pin holes in the backplate, and virtually every 1988 photo I can find has them too. It's like 88 seat units with the 3 slats (shark gills) that there seems to be no part number for!
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Andy.
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All interesting developments. My first thought is: IF there are not knock pin holes how do you adjust the RC Valves. So I looked into the R2J Supplement of the Workshop Manual and on Page 271 you find this describing how you lock the system at the pulley with a 3mm screw!

And then, just to throw more confusion into the mix, this is the MC16 section...


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Yeah...I guess the danger is not knowing the specific differences (if any) of the two methods of making the adjustments. I'd be willing to go with the non-knock hole process by using the pulley instead of the knock holes...however I ordered one of those T2 Racing pulleys because mine is a little bent out of shape and anyway the T2 ones allege to produce more bottom end they say "By changing the stock characteristics and making the RC valve movement wider, we are trying to increase the torque from the bottom to the top!!!...but note these pulleys don't have a hole for a 3mm locking bolt or screw.



I'm very interested to try the bike without the RC Valve operating and if it is indeed more two-strokey then I'm all for it. (As long as it doesn't high side me to the stars)

With the weather promising 0% rain I had no choice but to fit the brand new OEM petcock (the original had a Niagara Falls of fuel spewing out of it and there seemed to be no way to get it reconditioned)....


Work out how to hold the servo cables in place in order to keep the valves fully open..I came up with this...bicycle speedometer spoke magnets...



...so the pointers are aligned on the brackets....
Front

Rear


....fit the tank, put on the number plate,


refit most of the bodywork and go...


It ran OK. Just ok. It's all fine down in the bottom of the rev range and ticks over wonderfully at the lights, but it was not keen to go beyond 6,000 rpm unless I held it quarter throttle and let it climb up there....when...yes...the power would come on and almost lift the wheel...but I couldn't crack it open and expect it to accelerate or it would bog down and feel like it would just run on one cylinder.

I think there are a few reasons for this behaviour. (Note running fully stock air box with filter)

1- Fuel still has some oil in it. Made a 50:1 mix to be nice to the engine before the oil pump kicked in- which it did... so I added a gallon to the tank but there's still an element of oil in there.
2- As you know I'm running without the RC Servo which is on holiday in Japan- valves are fixed in fully open position which I think is when the pointers line up. Could it be that? Probably not helping.
3- To compensate running with these after market pipes...the Tyga's...I thought I should upjet the mains from standard of 130 & 132 to 135 & 138 because I didn't want it to run lean and risk a seize. Maybe that was not necessary. I have a feeling that's what it is- I have it too rich. I didn't do a specific plug chop but took out the plugs for a look see and - they aren't perfect- a bit rich- but I've seen worse. I should really run WFO for a moment and then do a chop- but the bike doesn't want to cooperate.

This is the jetting that was originally installed....130 up to 135 seems an odd jump but I couldn't find 134's or 136's.
Keihin TA20A
No.1
Main 130 (Now 135)
Slow 38
Needle BPD, Power Jet 70
No. 2
Main 132 (Now 138)
Slow 38S
Needle BPE, Power Jet 75



for example here's the selection available from Tyga...maybe they don't make 134's or 136's. Searching



4. It's also running pretty cool. That T2 Racing radiator https://t2-r.ocnk.net/product/497 seems bigger but the size is the same as the stock radiator in terms of length, width and thickness. The difference is the number of the radiator core 'stages' is increased to 31 compared to 25 for the stock radiator. Temperature guage indicates it to be at about 60-70ºC...which looks low on the dial.


It definitely got better throughout the run which must've been about 30miles.

FRONT (135 Main)


REAR (138 Main)


Conclusion: Before I do any more riding on it...
-wait for the RC Servo to come back.
-consider rejetting back to standard OR....take the top off the airfilter box just to see if it makes ANY difference. would be amazing if it did.

BEFORE

AFTER...and there's zero leaks.

Great that it was a [relatively] successful first run... and yeah, you'll need to keep the revs up with the RC Valves pinned open. It really is incredible, the difference operational valves make, and how tractable the NSR is with them.

One big no-no I have on the open forums is jetting discussion. I had a really bad experience many moons ago, where a complete bell-end tried to hold me personally responsible for using settings posted by another forum user for their bike, and consequently seized the motor! Threatened a law suit and all sorts. Bit of a pain, I know, but maybe I'll open a "Setup" discussion area, restricted to Members?

There will be a stack of HRC settings on the new site, from SP to F3 for all models, but they will still only be base settings to work from.

Coming soon....



That's the last 1/8th of the carburetion page... with all the info panes closed!
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Andy.
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That's going to be the holy grail of NSR information. Lot of hours there. Looking forward to it.

Totally get it about the jetting- (and what a w****r). The variables are infinite- trying to pin down an exact jetting plan is like juggling porridge. As far as I'm concerned to have any kind of talent in that area is akin to understanding black magic. Can you imagine what it was like in the 90's working on the NSR500 where there was more at stake than just showing off in front of the chip shop? Jeremy Burgess was one of those people who could do it. The other day these landed in my mailbox. Mr Burgess gave them to a friend of mine, who, once he saw what I've been working on, passed them on to me. The real deal mechanics gloves from that era.


They even have the rubbery bits on the palm and fingers..


Work is calling so I'll be away but hopefully by the time I get back the servo will be returned and I'll get it out for another run....one that will have the needle tickling the redline and the front wheel pawing the air.....well...one can dream about it..

It's great that you've got back to a running bike. I expect that the servo will make a huge difference. Then some refining.
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