Ton up SR250: 100mph, 100kg, 30hp

der_nanno

Faster!
Haha it's proving more difficult than thought but I'll think I'll get to the 74 mark - your bathing suit weight :p
Hahaha, you flyweight - there's a reason, why I am tuning XV1000s with similar ideas. *cough* trying to get below 90 again... (but also slightly bigger)

Btw.: Fell over your 95 vs. 98 question - I personally aim to be able to run an engine on 95, because if you get into knock-territory, you can just pour in some 98/100 octane fuel and fight detonation the easy way, without elaborate ignition tricks or jetting overly rich. If you're on 98 already you have to get some expensive octane boosters and may run into all sorts of issues that come from the "magic sauce".
 

JadusMotorcycleParts

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It's fun to look at pix of the old board-trackers and the positions they would assume to eek out those last few MPH on the straights. One trick I can verify from testing on my 883 was the left hand off of the grip and just hanging on with the right, and then using the passenger pegs for the feet.
You see all the flat track racers doing that trick with holding the left fork stanchion down the straights to be a little more streamlined. Hard core!
 

JadusMotorcycleParts

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Well, I have mentioned "bathing suit" for a reason ;)
There is always Rollie Free's way of doing things :D

Your SR250 looks sleek :D
Thanks! Haha well that is the very literal interpretation of bathing suit weight. I don't know if I am ballsy enough to try that! That is a great story and that image became so legendary.
 

JadusMotorcycleParts

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Hahaha, you flyweight - there's a reason, why I am tuning XV1000s with similar ideas. *cough* trying to get below 90 again... (but also slightly bigger)

Btw.: Fell over your 95 vs. 98 question - I personally aim to be able to run an engine on 95, because if you get into knock-territory, you can just pour in some 98/100 octane fuel and fight detonation the easy way, without elaborate ignition tricks or jetting overly rich. If you're on 98 already you have to get some expensive octane boosters and may run into all sorts of issues that come from the "magic sauce".
Haha, next projects will be based on bigger bikes, then I won't need to think about weight as much (including mine ha).

I didn't change to 98 for knock reasons, the engine ran really well on 95 when I first started and rode it. However, since then, the ethanol content in 95 went from 5% to 10% in Europe and that is why I changed to 98 - which still only has 5% ethanol. What are your thoughts on that?
 

der_nanno

Faster!
What are your thoughts on that?
Ethanol is your friend. Your new best friend. A friend with benefits so to speak. Its knock-retention capabilities vastly outclass all the compounds that were before it. Ethanol itself is not much a problem if you drain your carb(s) once you plan to park the bike longer than a week or so. (I installed manual petcocks amongst other reasons to be able to empty out the carbs on the last ride, when I know I am going to switch to one of my other bikes.)

Which is also why high ethanol-content fuel is really good for non-naturally aspirated engines as it runs cooler and prevents knock allowing you to get away with about double the boost on stock engines (i.e. up to one bar in my case) or run significantly higher compression ratios in turbo engines (10:1 instead of 8:1) on what is essentially spiced up pump gas.

In short: yep, I love ethanol in fuel. All you have to do, is take your (carb-)maintenance a bit more seriously.
 

JadusMotorcycleParts

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Ethanol is your friend. Your new best friend. A friend with benefits so to speak. Its knock-retention capabilities vastly outclass all the compounds that were before it. Ethanol itself is not much a problem if you drain your carb(s) once you plan to park the bike longer than a week or so. (I installed manual petcocks amongst other reasons to be able to empty out the carbs on the last ride, when I know I am going to switch to one of my other bikes.)

Which is also why high ethanol-content fuel is really good for non-naturally aspirated engines as it runs cooler and prevents knock allowing you to get away with about double the boost on stock engines (i.e. up to one bar in my case) or run significantly higher compression ratios in turbo engines (10:1 instead of 8:1) on what is essentially spiced up pump gas.

In short: yep, I love ethanol in fuel. All you have to do, is take your (carb-)maintenance a bit more seriously.

Thanks for your input man, that is really good feedback. I have watched a whole bunch of videos about using E85 as a performance fuel for performance cars, especially turbo and supercharged ones. I guess it means the same for E10 fuel only to a slightly lesser degree.

I see what you mean about draining carbs and taking that seriously, however, I would be more concerned about ethanol being hygroscopic and taking up water in the tank and other parts of the fuel system and then start rusting them. Or is that not likely to happen? Most places I have read also name it's corrosive properties, wreaking havoc on parts.

I wanted to get to the bottom of this so I read a few articles as well. It seams that, like you say, E10 would have even more detonation preventing capabilities than premium 98/E5 and has an effective RON of 105! So that can be considered a positive thing. However, it is less energy dense, meaning more of it needs to be burned to achieve the same output, meaning the jetting in the carb would need to be adjusted (larger jets) to compensate. This could be considered negative.

I think for consistencies sake and to save time with jetting (get all jetting right for one fuel type), I will stick with 98 for now :D
 

JadusMotorcycleParts

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I have now ridden the bike 120km and decided it was time to change the oil and filter, adjust the valves and re-tighten the head bolts. The head bolts hadn't budged and were still at the same torque. The valves tappets however needed some slight adjustment - both on the intake and exhaust. Looking into the head everything seems to be lapping in nicely with each other - cam and rocker surfaces. The oil seemed very clean, as did the oil filter and oil pick up gauze, so that is all positive.

Then when closely inspecting and cleaning the magnetic oil plug, I found a couple of tiny hard metal particles/filings. I have no idea what they have come from or if they have caused any damage anywhere, but I sure am glad the magnet picked them up! Well worth having developed this part! I guess time will tell if there is any internal damage.

I also swapped out the M8 tank bracket bolt from a 12mm hex to a 6mm flanged allen bolt - so that both the seat and the tank can be removed with the same tool :D There you can see the automotive fuse conversion done as well - very convenient.
 

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JerryAssburger

Been Around the Block
I have now ridden the bike 120km and decided it was time to change the oil and filter, adjust the valves and re-tighten the head bolts. The head bolts hadn't budged and were still at the same torque. The valves tappets however needed some slight adjustment - both on the intake and exhaust. Looking into the head everything seems to be lapping in nicely with each other - cam and rocker surfaces. The oil seemed very clean, as did the oil filter and oil pick up gauze, so that is all positive.

Then when closely inspecting and cleaning the magnetic oil plug, I found a couple of tiny hard metal particles/filings. I have no idea what they have come from or if they have caused any damage anywhere, but I sure am glad the magnet picked them up! Well worth having developed this part! I guess time will tell if there is any internal damage.

I also swapped out the M8 tank bracket bolt from a 12mm hex to a 6mm flanged allen bolt - so that both the seat and the tank can be removed with the same tool :D There you can see the automotive fuse conversion done as well - very convenient.
That bike looks so sharp. I am rapidly becoming a fan of SR250s.
 

der_nanno

Faster!
I see what you mean about draining carbs and taking that seriously, however, I would be more concerned about ethanol being hygroscopic and taking up water in the tank and other parts of the fuel system and then start rusting them. Or is that not likely to happen? Most places I have read also name it's corrosive properties, wreaking havoc on parts.
:D
I haven't noticed anything rust-related in any of my fuelt tanks, so from an engineering viewpoint I totally agree, in practice I wasn't able to witness any conclusive results though...
 

JadusMotorcycleParts

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https://www.rideapart.com/news/254553/how-to-set-a-land-speed-record-on-a-3200-motorcycle/
I think this is worth a look it may just make you think of something.
They did offer for sale a 300cc LSR version the more you paid the closer to the true Land Speed Record spec you got. I thought at the time they would end up collectable, but I don't no if any were actually sold.
That was a really awesome read! I love it, thanks for sharing. There are quite a few similarities with the mods I have done. Cool to see that from 229cc they got 23hp and 95mph (albeit in quite a prone position). Hopefully I can get closer to 30hp from 263cc and 100mph (in a lesser prone position)!

I was actually booked in for a day of dyno testing this weekend but had to reschedule because other things came in the way. I'll re book it once I have had a chance to test more myself and get the O2 sensor set up installed. I'll take the chance to get it registered again too - so I can ride around with good conscience ;)
 

gt alex

Been Around the Block
That was a really awesome read! I love it, thanks for sharing. There are quite a few similarities with the mods I have done. Cool to see that from 229cc they got 23hp and 95mph (albeit in quite a prone position). Hopefully I can get closer to 30hp from 263cc and 100mph (in a lesser prone position)!

I was actually booked in for a day of dyno testing this weekend but had to reschedule because other things came in the way. I'll re book it once I have had a chance to test more myself and get the O2 sensor set up installed. I'll take the chance to get it registered again too - so I can ride around with good conscience ;)
It's a funny thing I never seem to make it to the first time I book for a dyno, always something happens.
I had a suspension business and I was asked to cast an eye over a salt lake rocket car.
The first thing that came to mind was, this thing is very heavy, not what I expected.
I was told weight alone has no effect on top speed, It's power, wind drag and roll resistance.
It does affect how long it takes to get there.
I was told weight is a plus at 600mph because gravity is the only force holding you on terra firma.
It may or may not be true but I believe cafe racers got lower and lower to reduce frontal area in the pursuit of top end. e.g. ton up
 

JadusMotorcycleParts

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It's a funny thing I never seem to make it to the first time I book for a dyno, always something happens.
I was told weight alone has no effect on top speed, It's power, wind drag and roll resistance.
It does affect how long it takes to get there.
It may or may not be true but I believe cafe racers got lower and lower to reduce frontal area in the pursuit of top end. e.g. ton up
Yeah, I hope to get shit together for being able to dyno test soon.

Agreed, weight savings will not help so much for top speed, but when you only have 804m (1/2 mile) to get there, quicker acceleration will help. Weight savings has also made the bike much better handling and more responsive, so not all is lost.

Yepp, agreed re- cafe racers!
 

JadusMotorcycleParts

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I have mentioned it somewhere early on in this thread somewhere that I am kinda hoping to achieve what the Ducati Mach 1 - 3 250cc singles achieved: 28hp, and even 110mph! And that was without a fairing (which I really hope to avoid needing to fall back on).

Here are some specs:
https://www.motorcyclespecs.co.za/model/ducati/ducati_250_mach_1.htm
https://www.motorcyclespecs.co.za/model/ducati/ducati_250_mark_3.htm

And a really nice video about them/one of them:

Lastly, this was an inspiring read that came up in my feed today, super cool!
https://www.bikebound.com/2021/05/2...Lk4rjAG-j8A7GfOD-U8RSrz76iCQ19oN4o18PXSAXCKmo
 

JadusMotorcycleParts

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I couldn't drop the E10 fuel thing... Here are a couple of great videos about it. I really like how this guy is so thorough with his testing:


 

JerryAssburger

Been Around the Block
I couldn't drop the E10 fuel thing... Here are a couple of great videos about it. I really like how this guy is so thorough with his testing:


Fascinating stuff!

I remember the "Gasohol Days" in the early 80's. It would change a perfectly fine running car into a car whos fuel system had some sort of petro/bio snot running through it's filters. Back then, their excuse was, "...the new fuel cleans so well, it's knocking loose all the junk in your tank." You mean junk like, the rubber, metal, and plastic that my fuel system is built from?!?
 

JadusMotorcycleParts

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The 3 main goals of this project were/are:

- Weight: 100kg
- Power: 30hp
- Speed: 100mph

Unfortunately, I have not yet met those goals. But the project is not over yet either. So hopefully soon enough I'll get some dyno time booked again and the 7th of May speed test was postponed (by me) until mid June. So there is still an opportunity there to get an official speed. And I should be able to weigh the damn thing - I'll try to do that this week.

Another goal for the project that was more of a given than a focus was to get the bike finished and road legal again. At least this goal, as of this week is now achieved! Wihoo! The bike failed on a couple small things on the first visit - LED headlamp not allowed (does not form a proper light 'casting'/'throw') and registration plate lighting missing. Once those two things were fixed, the second visit yielded an approved bike.

A cool thing in Sweden is that bikes and cars that are 30+ years old are not charged road tax and are only required to get inspected every second year - as opposed to every year. On top of that, motorcycles that are 40+ years old and cars that are 50+ years old are not legally required to be inspected ever again! I guess they figure if you own a classic bike or car you kind of know what you're doing (or gotten yourself into) and that you'll keep the machine in good operating order. Anyway, this bike being a 1983 model no longer needs to be inspected ever again - so I am chuffed :) The test engineer thought it was funny to write that the next date for inspection would be the year 2099 - well past my used by date he said haha.
 

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JadusMotorcycleParts

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Some of the number goals might be a stretch but I am absolutely confident I can get 160kph. Will it be a first for an SR250? Maybe not - if you know of anyone doing it, please point me in their direction :D 100kg, possibly, 110kg, definitely. 30hp? At the crank, yes, at the wheel, maybe 26!
Had to dig this post up from the first page of this thread, just to remind myself what I was thinking. This post is dated Aug 20, 2017 - 5 years and one month ago :oops:
 

JadusMotorcycleParts

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I managed to weigh the thing this week, that is why I wanted to check what I was thinking back in 2017 haha

I rode onto a large industrial scale down at the port used to weigh grain trucks and it said the bike weighed 120kg! So I didn't trust that, it probably has a tolerance of +/-10-20kg or something.

Instead I bought a bathroom scale and 3D printed a couple of plates so that all three ground contact points of the bike were on the same level, then took a weight at each of those contact points. I had seen many other people on other motorbike forums using this method so I thought I'd give it a try. The pictures do the speaking.

I drained the fuel from the tank but not the 1.7l of engine oil which according to this site weighs 1.5kg.

So the weight of the bike is:

Weight front wheel: 41.65kg
Weight rear wheel: 41.35kg
Weight side stand: 28.85kg

Minus the 1.5kg for the oil leaves a dry weight of = 110.35kg

Plus 5l of fuel (1/2 tank) using this calculator = 3.69kg

Making for a wet weight of = 115.54kg (which is close to what the industrial scale said!)

I must say I am surprised and somewhat disappointed. You have all seen the lengths I have gone to lose weight off of this thing. I though a 110kg wet weight would have been possible - therefor closer to a 100-102kg dry weight. I am not 100% sure what the weight of the bike going in was but if you are to believe the manual and spec sheets, it would have been 130kg wet (oil in, 1/2 tank of fuel). Did I only manage to lose 15ish kg of weight?!

My conclusion is that I am probably one of the few anal people who actually go to these lengths to weigh their bikes and that many people claiming they have 'trimmed 30kg' from their bikes have not actually weighed their bikes before and after and probably confuse wet and dry weights. However, maybe there is more weight to be lost on bigger bikes? Also, again, that BikeExif article about the custom SR250 weighing 80kg is just plain bs. Haha I am still hung up on that straight out lie.
 

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