Yamaha SR250 - A clean standard build

One of the first things I used to do when I got a new bike was to play around with the ignition timing. Generally speaking, most bikes can get a bit livelier with a few degrees advanced from stock.


Pretty easy to do on an in line 4 because they usually have the pick-ups on the end of the crank.
 
hillsy said:
One of the first things I used to do when I got a new bike was to play around with the ignition timing. Generally speaking, most bikes can get a bit livelier with a few degrees advanced from stock.
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Awesome man! Good to hear from someone who has tried it :) I will definitely give it a go. Cheers
 
Back in Sweden now and looking forward to getting back into the project.

Was poking around on the internet today looking at SR stuff in Spanish - sooo much stuff out there in Spanish. Who knew the SR was produced at the Spanish factory until 2002 and at the Mexican factory until 2014?!

Also found this little chart that shows the SR250's power output - which confirms previous thoughts/investigations. Translation from Spanish =

_ Claimed output: 20 hp
_ Rear wheel output: 13.6 hp
_ Real engine output: 18.2 hp
 

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I'd buy that bracket for sure. These bikes are tuned for emissions and not power. That being said, 5° of timing with a hopped up motor might make a difference. Say it made 1bhp difference. I doubt you'd feel it. But a better running motor is a better running motor.
 
cosworth said:
I'd buy that bracket for sure. These bikes are tuned for emissions and not power. That being said, 5° of timing with a hopped up motor might make a difference. Say it made 1bhp difference. I doubt you'd feel it. But a better running motor is a better running motor.
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Sweet, thanks for the vote of confidence. I think if it made 1bhp difference it would be great - that would be a 7.5% increase in power haha. Then like you say, the engine might be running cleaner too. Despite what a lot of literature says, these engines dont have a bore of 75mm and displace 249cc, rather they have a 73.5mm bore and displace 239cc, which means the stated compression ratio of 9.2:1 is actually 8.9:1 which should allow for the 5 degrees increase in timing and make it perform better without detonation. Provided the octane of the fuel is sufficient - say 95 here in Sweden.
 
I collected all of the nuts and bolts and various other components today that I want to get black zinc plated. There is a mob locally that can do it so I'll see what they say about the larger items and then see what the results are like!
 

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I've had a lot of zinc and black zinc plating done. If you want a great finish on the larger pieces sand and polish them prior to plating. I usually polish or at least run under a wire brush, any large parts I have plated and large bolt heads that I know are going to be very visible. I'll try and find some of my pics for examples.

Also, if any of the pieces are chrome plated, the chrome will need to be completely removed prior to plating.
 
i wonder if any virago 500 parts interchange ? very slight dif in bore-stroke but maybe cam train parts ?
 
JohnGoFast said:
I've had a lot of zinc and black zinc plating done. If you want a great finish on the larger pieces sand and polish them prior to plating. I usually polish or at least run under a wire brush, any large parts I have plated and large bolt heads that I know are going to be very visible. I'll try and find some of my pics for examples.

Also, if any of the pieces are chrome plated, the chrome will need to be completely removed prior to plating.
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Thanks for the tips John. I was hoping that the chrome and the other already existing finishes would be removed in some kind of chemical process prior to being re-plated? And wouldn't that be the case for any grease or rust on the parts? I have no experience with this! When you say to sand/polish the parts for best results, does that mean the parts come up more shiny? Ie, if you dont do it, does the finish diminish in quality or just lust? Cheers :)
 
xb33bsa said:
i wonder if any virago 500 parts interchange ? very slight dif in bore-stroke but maybe cam train parts ?
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Good idea! Not sure though, just had a quick look at cams - dont seem like they are interchangeable. I'll look into pistons though - for a big bore perhaps.
 
Looks like maybe an oversize Virago 535 piston could work - 77mm bore giving 260cc - a 10% displacement increase roughly. Would need to buy one and measure it all up and that.

As for cams, I think it would be best to get the tt250 regrind from webcamshaft - the No 388. I will do that for the next build but hoping not to crack the engine for this build if I dont have too.
 
I got the chance to print a couple of prototypes of the ignition brackets I drew up in CAD. Then I was able to do a bit of a test fit/trial install. I want it to be as easy as possible so any body could do it with just a screw driver, a drill and some patience! Haha.

The first prototypes showed I needed to adjust the shape slightly so it fit easier and was easier to locate - these are the ones in the pictures. I had to chop them up a bit to make them fit. The second prototype was pretty much spot on. So now I'll draw up some dimensional drawings and get them made in aluminium so I can test it all properly :)

Originally I was hoping that the kit could be installed without any modifications at all, but I just couldn't get it to work. Anyway, now all that is required is a slight countersink to one of the mounts. This allows an M3 bolt to sit flush on the perch. The countersink is achieved with a 6.5mm drill tip, which I figure most DIY guys would have?
 

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JadusMotorcycleParts said:
Sweet, thanks for the vote of confidence. I think if it made 1bhp difference it would be great - that would be a 7.5% increase in power haha. Then like you say, the engine might be running cleaner too. Despite what a lot of literature says, these engines dont have a bore of 75mm and displace 249cc, rather they have a 73.5mm bore and displace 239cc, which means the stated compression ratio of 9.2:1 is actually 8.9:1 which should allow for the 5 degrees increase in timing and make it perform better without detonation. Provided the octane of the fuel is sufficient - say 95 here in Sweden.
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Sort of. There are two motors. One has 239cc, one has 249cc. The North American bikes are all 249cc.
 
cosworth said:
Sort of. There are two motors. One has 239cc, one has 249cc. The North American bikes are all 249cc.
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Aha, thanks for the info. That would be the bikes from '80 - '83 right? Those bikes dont leave much room for a big bore then huh. Unless of coarse the crankcases are opened up for a new sleeve. I have read about 5 or 6 projects where people have done it but it just seems like so much work, and work that needs to be outsourced to specialists as well. I was hoping to develop a big bore kit later down the track - one that just required re-boring the sleeve. Gotta rethink that one now!
 
I received the new and updated rear frame loop sample last week. Then I test fit it and gave it the go-ahead for production.

Today I had the chance to weld in place the old one I had so I didn't waste it. Just welded the outside seams for cosmetics, otherwise it is not load bearing or critical in any other way.

Once that was done I fired up the compressor and pot blaster and blasted the frame. Damn what a mission. I must be doing something wrong because it took a couple of hours at least. Doesn't help that the compressor only just keeps up and I have to wait for it to cycle every few minutes! Haha
 

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Yesterday I picked up the parts from the platers and they look awesome. Very much worth the drive to take them there. It was cool to see how they hang the small details as well. I just presumed they would be barrel plated but the guy said they hang everything. He also expects me to do the wire tying next time I take stuff to him ;)
 

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Received the metal ignition advance bracket prototypes today. They look sweet - looking forward to testing them :)
 

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grcamna5 said:
When you had those parts 'plated' black,is that a black-chrome plating?
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To my understanding they are electroplated with zinc first, then are passivized. Which could also be called black chromated zinc I guess... It seems like a pretty hard surface anyway :D
 
JadusMotorcycleParts said:
To my understanding they are electroplated with zinc first, then are passivized. Which could also be called black chromated zinc I guess... It seems like a pretty hard surface anyway :D
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Can they dip mag wheels
 
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