Hi guys,

In the process of rebuilding my MC21 SP and am after some guidance. "Eventually" GT Performance Engineering will have a job for me to build a top spec MC21 engine but at the moment, I just want the bike running.

For the bike so far, I have:
* HRC F3 Flywheel
* HRC F3 Clutch
* Harc-Pro Airbox
* A Brand New Crank
* HRC Reeds/kit (stufferes, spacers etc...)
*HRC F3 Carbs

I am looking at a Zeeltronic programmable ignition as my next purchase and the bike has had the wire splice completed, so no need (I believe) for the HRC Derestrictor.

I was looking at new high comp pistons, rods, heads etc... yet is this necessary?
Firstly, will all of the above work with minimal issues on a MC21 SP engine?
Are there any key call outs with the installation of the above items of concerns you would have? (I.e. it won't work, reduced power, unnecessary etc...)

I am trying to have a top quality build with what I have but am keen for further insight as you UK lads know your business! I wish Australia wasn't so bloody far away as I would have had Andy and the lads already make me something pretty spesh.

Any thoughts, help, guidance or ridicule would be appreciated
This will be a Rothmans Australia Special
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Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22

What will the bike be used for? Street/track or both? I don't see an exhaust system on your list so you may want to consider that. I would be hesitant to increase the compresion on the NSR unless you plan on running suitable race fuel (not pump fuel) even then i imagine the performance gain might not be worth it from a reliability stand point.
IMO getiing the bike Jettied correctly will be the key, and finding someone with the right experience and know how will be difficult in Melbourne, although some other Aussie members may be able to make some recomendations.

Here's how you can save yourself time, hassle, and money...

• HRC delimiter: not required - do the wiresplice
  
• Zeeltronic: not required* - the standard PGM-III is good for in excess of 70hp
  
• High compression: DON'T DO IT! - the NSR doesn't need, or like it!

Stock MC21 is 7.4:1. The above TT-F3 motor ran the HRC spec 7.9:1 and pump unleaded. No need to go wild with compression ratios on the NSR. It will just hit an RPM brick wall and detonate. You'll note there is no need to rev the knackers off of them either. Even the TT-F3 makes peak power below 12,000rpm.

Check the new crank is true. They're never as round as you would hope/expect, even from Honda. We true ours beyond HRC spec, and you can feel the difference through the footrests and less harsh over-rev. The motor will be significantly smoother with a well built crank!

*Programmable ignitions are more likely to be useful with 300 conversions, where they seem to respond more to tweaking the RC Valve and ignition timing.
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mtec666 wrote:What will the bike be used for? Street/track or both? I don't see an exhaust system on your list so you may want to consider that. I would be hesitant to increase the compresion on the NSR unless you plan on running suitable race fuel (not pump fuel) even then i imagine the performance gain might not be worth it from a reliability stand point.
IMO getiing the bike Jettied correctly will be the key, and finding someone with the right experience and know how will be difficult in Melbourne, although some other Aussie members may be able to make some recomendations.

Thanks for the insight MTec666. I'm already running TYGA Cans and Chambers.
This will be a road bike only. but happy to give it a crack on the track at some stage.

https://www.facebook.com/93NSR250RSPRebuild/photos/a.1726844320892391.1073741831.1724496354460521/1726844294225727/?type=1&theater

Yes, understand about the jetting. D**t would likely be the man but will check. Know HRC Jet Kits are "impossible" to locate!
I've found some 'jet kits' on buyee but don't want to waste money of they are sh*t as are not genuine. If not genuine, I'd prefer to stay clear.

I'm not going to play with compression.

Cheers
Popes
_________________
Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22

Andy wrote:Here's how you can save yourself time, hassle, and money...

• HRC delimiter: not required - do the wiresplice
  
• Zeeltronic: not required* - the standard PGM-III is good for in excess of 70hp
  
• High compression: DON'T DO IT! - the NSR doesn't need, or like it!

Stock MC21 is 7.4:1. The above TT-F3 motor ran the HRC spec 7.9:1 and pump unleaded. No need to go wild with compression ratios on the NSR. It will just hit an RPM brick wall and detonate. You'll note there is no need to rev the knackers off of them either. Even the TT-F3 makes peak power below 12,000rpm.

Check the new crank is true. They're never as round as you would hope/expect, even from Honda. We true ours beyond HRC spec, and you can feel the difference through the footrests and less harsh over-rev. The motor will be significantly smoother with a well built crank!

*Programmable ignitions are more likely to be useful with 300 conversions, where they seem to respond more to tweaking the RC Valve and ignition timing.

Thanks heaps for your time Andy.
I will be in touch at some stage about a professional build from you guys but at the moment, I'll use your below info to complete this one.


Re: Delimiter - The wire splice has been done successfully.
Re: Zeeltronic - ok, this is good to know. My only concern here is the reliability of a 23yo PGM over time. Understanding it can hold up to 70HP; is reliability there and are these reprogrammable? I've seen some 'suggestions' these can if blown. I'll keep an eye out for a spare I guess...
Re: Compression - Ok, good to know. I'm not too mechanically minded, more logical. So staying with the OEM Internals (Rods, Pistons) would maintain the compression, so this is the way to go I assume you're saying? If so, make sense. Maybe some new OEM pistons then as part of the build??

Re: The Crank. Really good to know - especially about the about ensuring it is true. My non-mechanical mind would think that from Honda it would have already been ready to go yet can understand the need to measure to ensure a perfect rotation to get the most out of the engine. Not sure what the actual HRC Specs are for a crank or how to go about that but, I'll ensure the webs on the side are like for like so there is no variation in the rotation.

Re the 300 conversions/Ignition - That's my next project
https://www.facebook.com/93NSR250RSPRebuild/photos/pcb.1733964240180399/1733964106847079/?type=3&theater

Thanks very much for your time Andy.

Cheers
Popes
_________________
Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22

Do you think the hrc fly wheel will keep your battery charged on a road bike ?

Yuri wrote:Do you think the hrc fly wheel will keep your battery charged on a road bike ?

Have I thought about that? Tbh, no I have not. What are your (or anyones) thoughts on this?
I'll be running a Speedcell 8 cell lithium 'at this stage'.
_________________
Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22

What about VHM or HRC heads?
_________________
Why do things simply when you can complicate them

You can put nxa or nx5 forks , ohlins rear suspention
Brembo calipers , Marchesini nxa wheels

Listen to what Andy says.

Cranks: They are very good out of the box, but by no means perfect. The big hammer will yield not just a smoother engine, but a few extra rpm too. It doesn't really make any more power, but will keep what power you have longer and more reliably.

Ignitions: The PGMIII is very good (for power) and also very intelligent. It's full 3D on the timing and does things that the Zeeltronic and/or the Ignitech do no and cannot do. I've already spent hours mapping the ignition and RC valve timing on the PGMIII (and others), and we (Stephen A'lee and I) spent hours mapping the air solenoids so that we could replicate it with the Ignitech. And what you end up with is something that's equal to the PGMIII. But there is of course the possibility of dialing it in for different tunes etc. And yes, as "The Grant" says, they're more effective for a bigger displacement motor than on the stock NSR250.

On other points.....nothing to add.

Cheers,

Matt.

Matt@TYGA wrote:Listen to what Andy says.

Cranks: They are very good out of the box, but by no means perfect. The big hammer will yield not just a smoother engine, but a few extra rpm too. It doesn't really make any more power, but will keep what power you have longer and more reliably.

Ignitions: The PGMIII is very good (for power) and also very intelligent. It's full 3D on the timing and does things that the Zeeltronic and/or the Ignitech do no and cannot do. I've already spent hours mapping the ignition and RC valve timing on the PGMIII (and others), and we (Stephen A'lee and I) spent hours mapping the air solenoids so that we could replicate it with the Ignitech. And what you end up with is something that's equal to the PGMIII. But there is of course the possibility of dialing it in for different tunes etc. And yes, as "The Grant" says, they're more effective for a bigger displacement motor than on the stock NSR250.

On other points.....nothing to add.

Cheers,

Matt.

Thanks Matt.

The Crank and bike is with an Australian racing legend - Don Stafford. He was really keen to be involved in this project and has said the crank has been adjusted and tested. Not sure to what degree the work has been done, but he is pretty happy with it.

I'm sticking with the PGMIII. I'll source a few others 'in case' but recall the mapping was pretty spot on before the chambers, reeds, heads etc... Given your feedback, it sounds like the PGM III will just pick up and adapt to the additions. Good to hear.

Thanks for your feedback Matt, it is appreciated.

Side note - How'd my Rothmans Tank end up for James's NSR250? Can't wait to see the finished product.

Cheers
Popes
_________________
Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22

Popes....how about trying fuel injection? We need someone to figure out a good set up for the rest to follow. Then we can adjust the mix from the dashboard.

ericandchi wrote:Popes....how about trying fuel injection? We need someone to figure out a good set up for the rest to follow. Then we can adjust the mix from the dashboard.

Haha!!

Maybe something to try on my next project 300... Not this baby.
_________________
Cheers
Popes

Owner - SP 2 Stroke Motorcycle Parts & Imports

Live 2 Ride
Ride 2 Live

Honda 00 VTR SP1
Honda 02 VTR SP2
Honda 93 NSR250R MC21 SP
Honda 02 NSR150 SP
(See. Pattern;) )
Suzuki 92 RM250
Aprilia 98 RS250 Mk 2
Suzuki RGV250 VJ22