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Author Topic: 1981 Yamaha SR250 Tracker style build  (Read 7566 times)

Offline Extreme_250

  • Posts: 47
Re: 1981 Yamaha SR250 Tracker style build
« Reply #50 on: Sep 16, 2017, 00:55:17 »

Offline zap2504

  • Posts: 346
Re: 1981 Yamaha SR250 Tracker style build
« Reply #51 on: Sep 16, 2017, 15:06:44 »
Got the bike legally on the road today! It took me a long time, but hey me being only 16 it takes time haha. Having some issues with it though. After riding it down the highway then shutting it off, it doesn't wanna start up again. Give it 15 minutes and it'll start up OK with some throttle. I checked the plug and it looked perfect, and it's getting spark when it's hot. Not sure what's wrong, it's never done this before. It doesn't wanna idle right either, keeps stalling at stop. The idle is either to high or to low, I cant seem to get a medium. Any ideas? Also, what is the standard setting for the idle mixture screw? Thanks for any help!
I believe the stock setup for the idle mix screw is 2 turns counterclockwise from lightly seated.
From your description it sounds like your carb's idle circuit needs to be cleaned (more throttle means adding air because it is too rich). Sometimes you can get away with putting some Seafoam in the full gas tank and going for a long ride to help clear out any gunk in the passages. Most times everything needs to come apart and the carb body needs to be immersed in a non-reactive (i.e., not super caustic that eats away the throttle shaft seals) carb cleaning solution (Pinesol and hot water, Yamaha carb cleaner and water, etc.) and agitated if possible (poor man's ultrasonic bath). Then rinse out, reassemble, readjust, reinstall.

Offline zap2504

  • Posts: 346
Re: 1981 Yamaha SR250 Tracker style build
« Reply #52 on: Sep 16, 2017, 15:18:05 »
On the list to buy:

Turn Signals
Tail Light
Front stop switch
Different seat
Chain and sprockets
RE turn signals - be wary of the LED versions. There was a recent comparison on AdvRider and the stock 1156 turn signal bulb was way brighter and more visible than any of the LED versions (plus you generally need to get a digital flasher unit due to the lack of resistance). I got a set of fake carbon fiber ones with 1156 bulbs, but had to extend the wiring and crimp on new bullet plugs.
RE tail light - lots of aftermarket "Lucas clones" available that look much better.
RE front stop switch - easily found but make sure the wires are the correct length.
RE crankcase breather - all the Emgo filter does is keep crud out of the crankcase - doesn't do anything positive over the OEM setup; the engine will still try to "breathe" in/out through that fairly tiny pipe on each stroke of the piston. I'm going to try (and Jadus will too) using a KrankVent between the vent pipe and airbox fitting. This will create a partial vacuum inside the crankcase and hopefully reduce pumping losses (it works real well for H-D engines that operate almost like a huge "thumper").
« Last Edit: Sep 16, 2017, 15:22:52 by zap2504 »

Offline zap2504

  • Posts: 346
Re: 1981 Yamaha SR250 Tracker style build
« Reply #53 on: Sep 16, 2017, 15:28:15 »
Any recommendations on where to find a decent quality tail light?
I was recently following a build of a Yamaha XV930R and he used a LED tail light/turn signal unit from TST Industries he really liked.
http://advrider.com/index.php?threads/a-rideable-xv920r-build.1239918/

Offline Extreme_250

  • Posts: 47
1981 Yamaha SR250 Tracker style build
« Reply #54 on: Sep 16, 2017, 23:41:26 »
I'll pull the carb off soon and give it a good cleaning. Feels great to have it on the road. Fun little bike! I bought some mini oval signals from Dime City Cycles and a hooded Lucas taillight. Love both so far! What a difference a taillight makes, LOL. That stock one was hideous! Thanks for all the help!!


« Last Edit: Sep 16, 2017, 23:42:58 by Extreme_250 »

Offline Extreme_250

  • Posts: 47
Re: 1981 Yamaha SR250 Tracker style build
« Reply #55 on: Sep 20, 2017, 19:26:32 »
Well after cleaning the carb, it seems to start up fine after a ride. Still can't get the idle right though. If I turn the idle speed screw up to where it won't die, when you rev it up and roll the throttle back it idles crazy high (the throttle cable isn't sticking). Can't get the idle to come down until you turn the idle screw back down, and then it won't idle without slight throttle. Any ideas? Thanks!

Offline JadusMotorcycleParts

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    • Jadus Motorcycle Parts
Re: 1981 Yamaha SR250 Tracker style build
« Reply #56 on: Sep 21, 2017, 02:39:53 »
Well after cleaning the carb, it seems to start up fine after a ride. Still can't get the idle right though. If I turn the idle speed screw up to where it won't die, when you rev it up and roll the throttle back it idles crazy high (the throttle cable isn't sticking). Can't get the idle to come down until you turn the idle screw back down, and then it won't idle without slight throttle. Any ideas? Thanks!

It is one of two things, or both.  You either have an air leak somewhere in your intake - perhaps in the rubber boot (worn?) or the vacuum hose connection. In which case needs to be fixed.  Or you need to adjust your idle mixture screw. Zap has mentioned it a few posts back but this is crucial.  The idle mixture screw is different to the idle screw (which it sounds like you are trying to adjust instead?).  As Zap said, this should be between 2.5 and 3.5 turns out from its seat.  If you are unfamiliar with this, jump on youtube or 1000,s of other threads about it  ;D

You could also check a few videos on how to detect an air leak - most involve spraying some fluid on the suspect areas of the intake and seeing if you idle speed changes.  Good luck!

Offline Extreme_250

  • Posts: 47
Re: 1981 Yamaha SR250 Tracker style build
« Reply #57 on: Sep 21, 2017, 11:41:59 »
That's what I figured it was (an air leak) but after testing with some some kind of spray (can't remember what I used) the idle speed never changed. I read that the mixture screw was supposed to be about 1 1/2 turns on, which is why I asked (because I thought it was supposed to be around 2.5 turns out). I'll mess with the idle mixture later and see if that fixes things. Thanks, Jadus!

Offline Extreme_250

  • Posts: 47
Re: 1981 Yamaha SR250 Tracker style build
« Reply #58 on: Sep 21, 2017, 16:35:09 »
I'm gonna have to order a new chain and sprockets, any recommendations on what brand to buy?




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Offline JadusMotorcycleParts

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Re: 1981 Yamaha SR250 Tracker style build
« Reply #59 on: Sep 26, 2017, 04:33:18 »
I'm gonna have to order a new chain and sprockets, any recommendations on what brand to buy?

Perhaps others can chime in here and have better suggestions...  But I have always gone with the cheapest on ebay and have never noticed any difference in quality.  This could be bad advice, but it is my experience.  I get the feeling sprockets and chains are one of those things that all come from about 2-3 different big factories in China, then get bought by 100s of different companies and rebranded as their own with some bullshite marketing spin in it.  Again, could be wrong.

O-ring chain?  Sure, they are good.  They will reduce your maintenance intervals and last longer.  Is the extra cost worth it?  How much riding do you/will you do?  If not so much, it's almost better just to get standard and clean and grease it every few times you ride.  If you ride a lot, the o-ring can be worth it.