Project Dave Moss CBR250RR MC22 racing in California

@simidau @Brizfox @danlar81

Guys, you interested in getting some pistons for your racebikes ?

 

Being in the race engine building game myself, the piston set prices are about what I'd expect for top quality, small run stuff.
Don't have a need at present though...
What interests me is your bearing contact.
Is there any chance of persuading Daido to release their master list of bearing fitments ?
I've never been able to find one.
They must have the info as to which motors a particular bearing set (specific ID,OD,width) will fit.
I'm aware of several motors for which I can no longer get shells, but with no ability to cross reference shell sizes it's bloody difficult.
An open source list of cross references would be a godsend.
Thanks

Greg Thomas New Zealand.

 

Hi Greg:
As much as that would be very cool, that won't happen. The only way I am able to get things done is to supply my own drawings. So, I have to Reverse Engineer the existing bearings, then create drawings of my own to submit. That way, I am not getting a "Honda Part", it is a bespoke "G-Force Part". As for what the bearings fit, that's up to me to tell them. They don't have any kind of list, or cross-reference list.

What you need to know is the outside diameter of the shaft, and the inside diameter of the hole. That will give you the bearing thickness. Then, you just have to peruse the service manuals for similar specs. But, there is so much more than that when you are talking bearings. The width of the bearing determines the contact patch size. The diameter of the shaft dictates the "bearing speed". That's the speed in which the shaft surface glides across the bearing surface. Too much speed, with too narrow a shell, creates too much heat. This would cause a bearing failure. Also, not enough oil flow would cause a bearing failure. So, the oil delivery holes is critical as well. Lastly, for main bearings, do you need a center groove as an oil channel, or do you keep it a solid surface? So, as you can see, a list would just not be enough.

The good news is, OE's generally stay consistent in their methods. So, stay with the same brand, and your chances are higher to find a cross-fit. The bad news is, if the bearings are NLA for one model, they will be NLA for all models. The bearing part number is treated independently when deciding to continue to manufacture the parts. Either the most recent vehicle that uses that part has to be 10 years old, or newer, or the continued sales of the parts have to be high enough to consider continuing to manufacture the part.

That's why I had to make my own drawings and get custom made bearings. It's a lot of work, and it's a lot of money invested for each model. So, just like the OEMs, I have to consider each model, and the potential vs definite sales behind each one. At 400 bearings per part style (rod bearings, outer mains, inner mains, etc.) that's over a 1,000 bearings per model. So, as you can see, I would need a lot of interest before I can consider making bearings for a particular model.

Mike Norman
G-Force Engine Development
www.mngforce.com
There is no such thing as "Too Fast"

 

Thanks Mike - worth a try anyway. I'm very familiar with the automotive aftermarket bearing suppliers catalogues, having used them many times - but with nothing similar for bikes it's hard.

As an aside I was searching in catalogues at an upmarket car restoration place local to me where i know the guys well.
Looking for a particular undersize for Yamaha TR1 big ends - small journal Chevy - and the machine shop foreman looked over my shoulder and said "thanks that's what i've been looking for, myself" - mains for a Maserati 250F GP car....

 

I won't speculate on the source factory of any of these parts, however it seems there is no shortage of NLA parts turning up on aliexpress.

For example there are plenty of VFR400 bearings available, with oversizes...

A metallurgist might at least be able to determine the quality of the materials used.

I will suggest caution on purchasing anything in more than minimum quantities to check quality, I've got a pair of 2KR (1-IN 1-EX) valves that are complete garbage, so happily I only purchased one of each.

 

http://2fiftycc.com/index.php?threads/interchangable-parts.9152/

nice co-incidence on timing

 

not to threadjack
@gregt - lots of online information available on megazip - on the XV1000 for expample
https://www.megazip.net/zapchasti-d...8542/crankshaft-piston-13492431#/il-317440202
models list - https://www.megazip.net/zapchasti-dlya-motocyklov/yamaha/xv1000-14519/xv1000-virago-28420

 

Well, I heard that Greame France was working with Chinese Suppliers to make replacement bearings. Greame is a good guy with a good reputation with the 400s. However, as you all know, the quality of the Chinese products is sketchy at best. Where-as, the bearings I am selling are made from the EXACT SAME supplier in Japan that made the original OEM parts. So, there is no concern about the quality of what you're getting.

'Nuff Said.

Mike Norman
G-Force Engine Development
www.mngforce.com
There is no such thing as "Too Fast"

 

[QUOTE=" However, as you all know, the quality of the Chinese products is sketchy at best." [/QUOTE]

Chinesium has wonderous properties... we also call it Smic ( pronounced schmick) - **** Made In China

 

Whats the estimated cost on the pistons out of curiosity? I was speaking with my dad about a racing engine rebuild during my birthday 5 days ago, however there is allot to consider here... If the pistons weight is different from stock then the cranks counter balance will need to be altered which depending on if (heavier or lighter) how hard it will be.
Also if the piton's are the stock size how would one go about re honing the used cylinders?
I am also curious how you plan to tackle the increased internal cylinder heat, the stock spark plugs already have a heat resistance of 9, do you intend to retard the timing to compensate?
It has been my experience with this engine that no matter what is done it always seems to lose top end, I think that Honda didn't hold back at all with this engine and the only gains (minimal) that are worth going for come from the replacing the stock muffler.
The only other thing that has come up but not officially done is replace the mechanical water pump with an electric pump to decrease the load on the engine.
I am interested in this and would pay depending on cost vs reward, I love the mc22 and would love more power if 55hp can be proven to be obtainable without increasing the displacement I would be willing to pay a good 2k AUD to do so, but any more than that would just be crazy...

 

Hi Damus:

While I appreciate your enthusiasm and interest in building the engine out, I have to say that you should definitely do some heavy reading. One of the best books is Sportbike Performance by Kevin Cameron. You can get that book here:
https://www.amazon.com/exec/obidos/ASIN/0760302294/typepad0c2-20

I've been doin' this a very, very long time. And, all of your concerns are good questions, but they are all handled, or not an issue (like the plugs). Have a gander at my blog to get a feel for my history and see some of the things we've been doing http://mngforce.typepad.com/nc450vdev/gforce-history.html What that History doesn't include was the last 3 years, where I was working as an Engineer for Honda in their IndyCar Engine Development division. All we did was design and build top-tier race engines all day long

If you are seriously interested in pistons, and really want help building the engine, I am always willing to help you out. With Dave Moss' engine, we were able to get power EVERYWHERE, including top-end, without high-compression pistons. As you can see from the graph, we made some very significant improvements for Dave from the first time he brought us the bike (green) to now (Red):


NOTICE:
No Spark Plugs were harmed in the making of this Engine.
The Ignition Timing was untouched to protect the innocent
The Cam Timing was not altered for prosperity.

In all seriousness, you can see that the engine responded very well to all of my work, which was purely aimed at reducing lsses due to friction. Pistons are usually the #1 change to get he most for your dollar, and we haven't even done that.......yet. I believe that pistons would push this engine very close to 55hp. And, if I time the cams (which requires quite a lot of work to make custom adjustable gears) we can get that hard drop in power at 15k to maintain height for at least another 1k~2k. Ignition timing may help even more.

Let me know if you are serious. I think I can help you build an MC-22 that you would want to keep forever. I have been a professional in the motorcycle industry since 1986. I have ridden almost all of the bikes made. But, the CBR250RR is BY FAR - HANDS DOWN - my favorite track bike I have ever ridden. And, that was Dave Moss' bike with the blue graph above. I haven't even ridden the bike with the new (red) engine. But, he assures me, "it rips"! He would have won the 250cc Superbike Championship this year had it not been for a stupid DNF.

Cheers

Mike Norman
G-Force Engine Development
www.mngforce.com
There is no such thing as "Too Fast"

 

That hard drop at 15 looks a lot like ignition to me. As you've raised the BMEP, it's become more significant and has more effect.
I've never seen the stock curve but I'd put money on it retarding around there.
I'm a KISS fan and would start with a straight line ignition and see what happens.

 

Well you have me excited! I'd love to hear everything and will take all the advice I can get!

 

Nope. You were on the right track with VE. The hard drop is due to the engine choking. Combination stock airbox, carbs and cams closing too early.

Mike Norman


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I'd just like to say to both @gregt and @Mngforce thank you for sharing your combined wisdom, it's nice to see engine work being accomplished with work

I used to read the motorcycle magazines, but tired of the project bikes which were merely a laundry list of damned expensive, name brand, go fast bits which usually only achieved the fastest wallet emptying ever for the sake of bragging rights and not much else that I could discern

 

BTW @Mngforce I don't know if there are enough similarities versus differences in piston specs - compression height, combustion chamber design, shape & compression ratio, not to mention valve placement between the three brands, but if the baby race bikes are to see a revival amongst the current crop of 250-300cc bikes in races...

perhaps there's an opening for pistons for:
FZR250R's 48mm bore STD
CBR250R's 48.5mm bore STD
ZXR250's 49mm bore STD
I believe all three see time on the track in races here, though I've no idea about the numbers and which ones are placing where...

Taking this a little further to enable them to compete on capacity with the 300's @+1mm overbore
FZR250 -> 300; bore - 52.6mm (+1mm) -> 53.5mm
CBR250 -> 300; bore - 53.1mm (+1mm) -> 54.0mm
ZXR250 -> 300; bore - 53.7mm (+1mm) -> 54.5mm

The above assumes that resleeving cylinders is do-able & feasible for the larger capacity

 

Ok, you know more about this motor than me, LOL.
I'm almost certainly older than you and been at it longer though, again, LOL. probably past it now (cough)

What are the carbs used - still CV's ? I've seen instances where at very high RPM the vacuum signal strength is insufficient to keep the slides up...Had a look down the throats at full noise on the dyno ?
Those gear drive Honda cams are a pain to work with - I've done an RC30 or two back in the day and moving things was a major job.

 

Yes still the stock CVS at this time. However, FCRs are on the "wish list". EFI was discussed but I don't feel it's worth the effort right now. I may change my mind however.

I want to make adjustable cam gears like I did with the NC-30/35. But, definitely a lot of work. I think that there was a lot of power gained at the low end. But, who uses the low end in racing? I would rather sacrifice that power to get better top end. So, retard the intakes. This could possibly help with the loss in signal strength for the CVs you witnessed. Also, I want to make sure the exhaust is open enough by BDC to have evacuated the cylinder as much as possible without causing pumping losses by closing too soon.

Still lots to do. Lots to do indeed.

Mike Norman


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Bore out the cast iron liner, then apply NikaSil (or equivalent playing) directly to the aluminum. That's my plan anyway.


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Im game to look at this. Can anyone send me Pistons for these bikes (used is fine) as they don't sell any of them in the USA?

Mike Norman


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