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Author Topic: '84 SR250 Garage build.  (Read 18212 times)

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #10 on: Apr 23, 2013, 22:08:44 »
Thanks Relax. All good now though I grabbed a few from the wreckers a while back.

As for the bike I have finally achieved the exhaust tone that I wanted. The muffler is a little too restrictive for my liking but as I still have the stock head pipe it is not that big of an issue. I filled one of the megaphone mufflers that a friend of mine gave me with steel wool and cut the old baffle that it had to make it less restrictive.
After the different concept baffles that were made and blow to bits I went back to the one that it had to begin with. I welded it in there as the first time I gave it a good rev it ended up a few meters away.
Once I get a custom header made I will consider opening up the baffle some to relieve the restriction a bit. Anyway here is a picture of the new setup.
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #11 on: Apr 26, 2013, 22:25:08 »
Alright so after a bit of test riding and tuning I seem to have a flat spot after 3/4 throttle. Now I know that I will need a larger jet because of the pod filter but I have decided to go another route and get a new carb all together. The current carb has a few issues and needs a rebuild but since it is old tech I am going to grab something a bit more modern. I have been looking at the Mikuni TM36 or the Oko K-104 36mm and cannot decided. The Oko is a reproduction of a Keihin PWK36 and is closer to my budget than the Mikuni.

Decisions decisions. 
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline DesmoBro

  • Posts: 2396
  • Busted Nut
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #12 on: Apr 26, 2013, 22:27:41 »
Just get a few jet sizes....don't you have a stock mikuni?
"I desire the things that will destroy me in the end"

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #13 on: Apr 27, 2013, 00:04:52 »
Yeah have the stock one. I guess I am just looking for excuses to stick a flatslide on it.

I should just grab some jets and work it out. I think the stock is a 125 so I guess a 127.5 and 130 would be the next two to try. What kind of info do you have on the carb Desmo. From what I know it is a Mikuni BS34. Just having trouble trying to find jets that don't have shipping on them more than the price. Australia is good like that.
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline DesmoBro

  • Posts: 2396
  • Busted Nut
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #14 on: Apr 27, 2013, 00:42:57 »
Not really sure where is good place to order them down unda... Jetsrus.com may have them but not sure about shipping
"I desire the things that will destroy me in the end"

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #15 on: Apr 27, 2013, 01:03:15 »
I pulled apart the carb and now I remember why I wanted a new one. A few screws are stuck but nothing a hacksaw and a flatblade screwdriver won't fix. I can't get at the top side of the carb because of the stripped screw heads. Anyway I stuck it it a tub of "General purpose degreaser" as it seems to strip everything away where as the carb cleaner I had did bugger all. This stuff is stripping the crappy paint off the carb that the cleaner did not.

The main jet is a 122.5 and the pilot 47.5. So not far off that 125 and 50 I thought they were. I ended up giving in and grabbing two main jets a 127.5 and 130 but they will be a way off yet as postage from the US takes around 3 weeks. See how she goes after this harsher chem bath.
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #16 on: Apr 27, 2013, 01:51:06 »
Finally got into the top. There was a fair bit of debris up there and I discovered another jet. After finding a better breakdown of the carb http://www.boats.net/parts/search/Yamaha/Motorcycle/1981/SR250TH/CARBURETOR/parts.html I found that is the Main jet and what I had though was the main appears to be a smaller main jet. So that would explain why it was choking at 3/4. I have to give the larger main a good clean but I cannot seem to find a size written on it yet. Back to it and once it is dry I will give it a go and come back with the results. Learning about new carbs is fun once you pass the "god I hope I don't fuck it" stage.
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #17 on: Apr 27, 2013, 03:52:43 »
Alright after all that it is a lot better but there is still a slight splutter. Seems to pick up a bit quicker and it is spluttering well after when it was. So I will be assuming that a size bigger jet is needed. I still don't know the size of the primary main but from what I can find it seems to be 140. I am thinking a 145 would be the go but I will wait and see. To bad for me that I already ordered those jets in 127.5 and 130. Ohh well that is the price I pay for being impatient.
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

Offline DesmoBro

  • Posts: 2396
  • Busted Nut
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #18 on: Apr 27, 2013, 11:27:38 »
All this talk about jets makes me want to ride this little beast!
"I desire the things that will destroy me in the end"

Offline Brodie

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  • Posts: 2091
  • Gold Coast, Queensland
Re: '84 SR250 Garage build. Solo Tracker now, Cafe later.
« Reply #19 on: Apr 29, 2013, 03:30:41 »
I have been giving the carb another clean today and found this guide which showed me a few thing I didn't know about the carb. http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf . The guide is for a gs1000 which has 4 BS34s so obviously a few things don't apply. I grabbed some heavy duty carb cleaner today and the stuff works to well it cleans the skin off my hand. Sadly it eats rubber so I need a new oring for the float valve seat which should be easy enough.

It also managed to clean the primary main jet away enough that I can make out it is a 160. So it looks like something else might be the problem. I did a bit of research and came across Crazypj's post about Emgo pods and CV carbs. Sure enough the boot was slightly covering the vacuum port and by my guess not allowing the slide to open far enough at full throttle. I am also having a problem with fuel leaking from the air intake but I will raise the float needle and see if that stops it.
« Last Edit: Apr 29, 2013, 23:51:33 by bvander »
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.