Building a race bike

Hi Vince,
Yes I have had dyno sim software for over 20 years now but the modern stuff is super good if you have the right package, mine is quite expensive but well worth the money for the work I do on it and the results have been good in practice also. although there is always bench testing and some adjustments to make.
The thing to remember with these things is. Crap in = Crap out. You really need to measure and flow test every last part and put in real figures or the complete sim will be a total guess. this in it's self is weeks of work but it really is worth the effort. You also need to do it if you are not using a computer as if you don't know your flow figures and gas speed etc how in hell can you figure out the other things. Life is a lot easier if we know what we are actually working with instead of guessing.
I have done a lot of guessing in the past and always regretted it.

Megaphones are very critical beasts and reverse cones need to be tailored to suit also or they can fuck things up as much as help.
Tapers are super critical in both exhaust pipes and inlet passages.

Best regards,
Jules
 
Hi Jules,

had also a good experience with exhausts and can confirm that even for standard engine configurations, there is a lot of room for improvement... I bought my 1000 SFC f.e. with a nice System, but unfortunately the pipes were not made out of stainless as it was a prototype. The system was so rusty at a point in time that it broke. I replaced it with what was available at that time and got a friend of mine completing it with a "super bike" style exhaust can. I immediately felt the loss of torque in midrange but thought I might have to change carb settings etc.

One day, I changed to Keihin Carbs and wanted to get them set up perfectly, so I asked a local shop to set them right on the dyno. He called me and said that he can not make them work any better, the loss in midrange is massive and he thinks everything points to the exhaust being the cause. So - I asked OCT to borrow me a standard exhaust to see if this cures it (and if so, sell it to me). Well - it did not... it improved it a bit, but the drop in midrange was still significant. OCT suggested to go to SR-Racing.de for an individual exhaust, which I did. The improvement was massive...

Scan10002.JPG
The difference is not so much the peak numbers, it is the change in low to midrange which was impressive and which improved rideability a lot...

Sepp (the owner at that time) was sure to improve it even further if he had more time (and the clutch actuation would last...), but I told him this is way more than I expected... As you said, the inlet is tappered, different carbs and the exhaust also has a different routing and a tapper build in. Sounds nice, runs nice - great street bike now ;-)
 
Loving this development chatter. Very interesting to read the outcome of some of the testing, such as the lack of cross-cylinder exhaust effect over 5k. I'll definitely throw a couple of exhaust options on the bike once it's dyno time. I've gone with my own hunch with smaller than std SFC header pipe ID. We shall see ...

My 39mm FCRs taper to 37mm through the initial part of the extended inlet tract and the port remains around that to the bowl area and 44mm OS valves. I want the final porting work done by someone with the right experience and equipment.
 
Hi all,
Nice and interesting comments, Lothar, your graph shows exactly whay I had on a 1929 2.4 litre 4 cylinder engine I developed some years back,
We got it up from 50hp standard to 115hp at the same rpm but with a big hole in the mid range torque curve where it was hardly better than std, this had the outer two exhaust ports and pipes working for cylinders 1 and 4 with 2/3 Siamesed like a Mini A series engine. The std philosophy on these is to have what is called a Long Centre Branch (LCB) for best power and torque and to take into account twice the volume of gasses entering this centre tube. Nope!!! This one wanted three pipes exactly the same length and not entering with a std collector as that didn't work satisfactorily either, but to enter like you see on old racing cars when the first cylinder comes out, sweeps round and tapered from the join with the second (centre pipe) and then the third pipe joins in a curve directly after that. (see picture) 30hp increase in the mid range and a perfect power curve ending in another 5hp on top. Like mentioned, nothing like testing to prove theories wrong.
But we need somewhere to start from don't we.

Regards,
Jules
 

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Nice New Final drive chain just arrived. Did (excuse the pun) a load of research on finding the strongest and lightest 520 chain possible.
Came up with this at 1103g and a tensile of 4050kg compared to the only stronger one on the market (ER) with a tensile of 4082kg but a weight of 1780g so a saving of over 700g spinning around at high speed. Well worth the saving! (out of interest most 520 chains that are used by the race boys with up to 200hp are rated at about 2700kg tensile.
The MX is a non O ring but will be lifed and replaced often anyway so not worried in the slightest about keeping out the dirt for years.

Julian
 

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Just out of interest what's the ballpark cost of the chain. Crazy race price? Mine usually go around $200ish oz.
 
I got the chains at about 100 euros each, bought 3 at once. 118 links as mine is running different sprockets than std and want some room to adjust to my needs.
Regards,
J
 
I did the same research Julian and settled on the heavier X-Ring 520 DID chain rated at 4082kg
Have 2 chains for each bike, depending on which track we are at and what gearing we wish to run I need either a short or one link longer chain
DID is good kit
 
Finding a currency converter that doest want to actually do a deal, took more time than I expected. So 100E is approx $170oz, so not nuts. I had visions of megabuck race costs for ever tiny thing
 
Vince. AMX superstores sell the full range of DID chains and generally have the full range in stock. Was only looking at them in my local one in Canberra a week ago.
Tom
 
I use Tsubaki, their top of the range one rated for Hyabusas, it has a chrome finish in 530 O ring. Their OZ head office is in Silverwater so reasonably close. Had a few issues with supply lately so DID might be next. Gota take the race blokes advice.
 
Vince said:
I use Tsubaki, their top of the range one rated for Hyabusas, it has a chrome finish in 530 O ring. Their OZ head office is in Silverwater so reasonably close. Had a few issues with supply lately so DID might be next. Gota take the race blokes advice.
Click to expand...
Just put one of these on the Corsa Vince, $150 👌🏼BAF0F891-9F99-4202-9E34-DCBBAF9BA7B0.jpegC5F7A3B9-2F2F-47B1-8F4F-62F44E1A35BF.jpeg
 
I did really consider the X ring chain but due to the fact that I am trying to get the weight to silly light levels, I thought it was worth the trouble.
Knowing it needs more maintenance will also make me pay attention to the chain more as I hate to DNF for silly reasons.

Regards,
J
 
I drive a normal high-quality DID chain WITHOUT O / X rings on the Eagle.

I also drive it far and, unfortunately, often longer distances in the rain.
With modern lubricants like HKS I don't see any difference to the O-ring chains on the other Laverdas. During a holiday of 2,500 - 3,000 km with a lot of mountains = higher loads and bad weather, you don't have to retighten the chain.
I lubricate 1-2 times on the way.

This is a gigantic difference compared to the older days, when you cooked the chains in a pot with Castrol chain fat on the camping gas stove.

Thomas aus LAU
 
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I used non O ring chains on my track bikes and on the SFC. Need of maintenance isn't a problem.
O ring chains on my street bikes which get lubed two or three times in their 25 000 km life and tensioned twice. Whatever's in the shop when I need one.

Paul
 
julian said:
I did really consider the X ring chain but due to the fact that I am trying to get the weight to silly light levels, I thought it was worth the trouble.
Knowing it needs more maintenance will also make me pay attention to the chain more as I hate to DNF for silly reasons.

Regards,
Click to expand...
julian said:
Nice New Final drive chain just arrived. Did (excuse the pun) a load of research on finding the strongest and lightest 520 chain possible.
Came up with this at 1103g and a tensile of 4050kg compared to the only stronger one on the market (ER) with a tensile of 4082kg but a weight of 1780g so a saving of over 700g spinning around at high speed. Well worth the saving! (out of interest most 520 chains that are used by the race boys with up to 200hp are rated at about 2700kg tensile.
The MX is a non O ring but will be lifed and replaced often anyway so not worried in the slightest about keeping out the dirt for years.

Julian
Click to expand...
Hi Julian
that chain will fit your bike , is cheap (50-70€) and with that lock easy to mount. with that price one can afford a couple of chains for different sprockets. And you do not need O rings as long you do not build a tourer. Well I have to say , my bike has just some 70HP rear wheel for 164 kg.
Cheers and good luck
Michael
C44E0ECE-F027-41F5-AC04-48768957AC84 by Michael Kurtz, auf Flickr
 
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