Yamaha SR250 - A clean standard build

JadusMotorcycleParts said:
So if it has to go (because the stock SR set up IS butt ugly), why not replace it with a proper filtered intake trumpet rather than just a clamp on filter - you might get back some of the power lost and maybe even (with a wish and a prayer) even get a small gain (up top only) ;)
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This has actually been accomplished by others I've seen (mostly on forums of 4-cyl bikes) where the OEM air box has been damaged beyond repair or removed by the PO and is NLA. Solutions have ranged from re-using the OEM velocity stacks/connecting boots that were in the original air box or adapting PVC piping from the carb intakes to good-quality individual aftermarket filters (like K&N) or to a home-brew plenum constructed from even larger diameter PVC pipe and a single filter. But the bottom line has been that you cannot accomplish the same "cafe racer tabloid look" (AKA empty frame triangle) without a decrease in performance (in the area that the bike will really be used) and a lot of work to even get it drivable in the upper range.
Maybe a future project to do a 3-D printed air box that looks good?
 
Holley and KeiHin are far from apples. I would sooner spit in the manifold than run a Holley, fuckin Carter AFB is a better mixer... JMO 8)

I have two CB750's with pods and both launch with more power than the cops allow... seems you are doing something wrong. I do agree it could be better with a stock box and a good after market filter. This subject will never be any different than the current election process, free or freeload. haaah!
 
Tune-A-Fish said:
Holley and KeiHin are far from apples. I would sooner spit in the manifold than run a Holley, fuckin Carter AFB is a better mixer... JMO 8)

I have two CB750's with pods and both launch with more power than the cops allow... seems you are doing something wrong. I do agree it could be better with a stock box and a good after market filter. This subject will never be any different than the current election process, free or freeload. haaah!
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My analogy is related to vacuum and velocity. Obviously they are very different, but the need to mix fuel and air appropriately is the same. Conditions must be matched.
 
Tune-A-Fish said:
I would sooner spit in the manifold than run a Holley, fuckin Carter AFB is a better mixer... JMO 8)
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As far as this statement, I'm not as hot and cold to compare the two. Except that Holley is waaaaaaay more tunable. I'm running a Holley on an Edelbrock manifold and happy to be there. I'd run a Demon before an Edelbrock (Carter) carb anyway.
 
I can tune a holley but I can't Tune-A-Fishy!

If you can't tune your holley it's because it's too big!

Same as bikes!

Velocity Velocity Velocity!

Over anal-eyes-ation!

Want a faster bike? Sell the 250!!!!!!!!!!!!!
 
Demon is a Holley init? I like fuel injection now so anything less is too much work.


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Looks like I've struck a nerve. I'll try and stay away from performance based discussions! I actually have a bigger, faster bike. But that's not the point now is it? We do this cos its fun and we love wasting money on two wheeled machines right?

On another note, I touched up some images of the engine as it is now showing off the bolt kit and the latest valve inspection covers 8)
 

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stroker crazy said:
Some numbers:
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Yeah that's a great article, love finding stuff like that. Posted it two pages ago in this thread ;)

Heres some real world numbers too: http://www.emeraldm3d.com/articles/emr-adj-length-intake/

Rather than theories and simulations :)
 
Started doing some more work on the carb too and noticed properly this time the JIS screws that doc_rat pointed out to me - the punched dot is a giveaway. Even though I have noticed it before, I never knew what it was. Cheers man.
 

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JadusMotorcycleParts said:
Looks like I've struck a nerve.
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Lighten up will ya. Just stirring some marbles in to the jelly.

I just came up with that. It's a metaphor. ;D

Engine looks great! What kind of oil will you be using... :-X
 
DohcBikes said:
Lighten up will ya. Just stirring some marbles in to the jelly.

I just came up with that. It's a metaphor. ;D

Engine looks great! What kind of oil will you be using... :-X
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Marbles aren't apples.
 
I commend you for putting together a bolt kit that is not stainless steel.
 
DohcBikes said:
Lighten up will ya. Just stirring some marbles in to the jelly.

I just came up with that. It's a metaphor. ;D

Engine looks great! What kind of oil will you be using... :-X
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Haha, you're a stirrer! I almost spat my coffee out when I read this comment of yours 'Over anal-eyes-ation!' lol You're right though, way over complicating a simple function... and only for a 250. Fun exercise though ;D
 
I have actually designed a version of these finned valve covers for the infamous TW200 as well. They were quite similar to the SR ones so I decided to buy a used set from ebay and transfer some of the minor dimensional and detail changes to make them. The cool thing is, these also fit the SR125 and the XT225. I would love to know if there was any interest for these... I rekon they would help with the TW200 (and the others) running hot. A known issue if you're going to be running on the highway for a stretch. I would get them made with a black anodized finish to match the TW200s black engine. 5-axis CNC machined 6063 billet aluminium 8)

Something cool that I just found out... They are still making the TW200! Exactly the same as it was when it was released back in 1987!

https://www.youtube.com/watch?v=iHPcYzRUTgo
 

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Looks awesome!

Maybe you could make some parts for the Honda 650 RFVC engine? Loads of guys are using those but I can't think of anything more than a new oil filter cover though..
 
Jadus please pm me with a price for the valve inspection caps.

FYI they will also fit YTM200 and YTM225 Three wheelers, as well as YFM200 YFM225 and YFM250 Moto4 ATV engines. So that's 5 more models over several years that you can market those to.

I am currently building a high compression big bore YTM225 engine, I'm gonna need a set.
 
Jadus, please PM me with a price for TW200 valve inspection caps.

You're right, the TW200 is largely unchanged since '87, with some notable exceptions, like deletion of the kicker, change to a disc brake on the front wheel and a more powerful stator. From a few feet away, the only difference you'd notice is colour.
 
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