'84 SR250 Cafe. PLANNING PHASE

I decided it was time to start planning the Cafe incarnation for my SR250. At the moment she is a sort of tracker/brat. I will just call it a bratracker for lack of a better term. I have a small reviving thread located here http://www.dotheton.com/forum/index.php?topic=45576.0 which has most of the details on what I have done to the bike so far. As I have no funds for the cafe build at the moment I thought it would be a good idea to start a planning thread so that I don't loose any of the ideas I may have. I will be updating this post with any new ideas I have or any better suggestions that more experienced people may have.

So my plan is to create a small engined cafe that will be used mainly for around town trips with a few 300km runs in between. I am not looking to create a show bike but something that I can have a hell of a lot of fun on. So I don't plan to bet spending 3 hours polishing the valve covers to a mirror finish. I am looking more for functionality then aesthetics and will be creating the bike to how I want. As I am in between jobs and looking for a new career don't expect to many update early on in this build.

Here is a rough list of what I have planned for the bike and a smaller list of what I have done already.

PLANNED
Mikuni TM34 carby
Cafe seat molded part over rear of tank
Piggyback style rear shock
GSX-R 600 1992 front end
TT250 Racing cam 286 duration
High Compression piston (Help if anyone knows what will fit)
Performance valve springs
Remove unneeded weight (from the rider as well)
Clip on bars
Acewell 2853 Multiguage
Add tubes to create a flat surface for the seat
Create battery tray between new tubes and original if there is space
Alluminium rims and SS spokes
Custom exhaust to replace stock "two tube" one
Lightened chain guard


DONE
Ballistic 4cell battery
"Megaphone Muffler" I need a baffle for this
Detab frame
40T rear sprocket to bring top speed closer to the ton
Velocity Stack
Replace center stand with side stand to lighten bike
Smaller headlight


Here is a picture of what she looks like now. The rear shocks I plan on getting will have to be longer to bring the rear end up higher. I plan on pushing the forks up in the triple but only enough to allow clip on bars to be attached. I would also like to put a smaller front rim on just to bring down the difference between the two. I don't have an order or a time limit so the mods may be far between for a while.

I would love to hear people opinions on what I should and should not do. I know the SR250 is no the best base for a cafe because of the rear frame shape but I would love to see this bike become something special.

I know it's been two months since you posted this, but how has that ballistic 4-cell been working out for you? I've been thinking of one for my 250, but I was thinking a single 250 cylinder would be tough for a little 4-cell to kick over. Seems to work for you?

Hey mate. Yeah this thread is slow as I have been saving most of my income. The 4cell is good but it is more of a battery for a bike you know will start first time without to many cranks. I have had to push start the bike once when riding as I was having idle problems and had to keep restarting the engine. After a bit of a ride it charged up nicely and has been fine since. Going to get some serious riding in soon so I will be able to tell you a bit more in a month or two.

Alright I have started to plan a fair bit more and have been revising and researching a lot.
I don't mind how my bike looks now and I have had a fair few people comment on it but it is just not quite what I am after.

The current plans are:
CB200 Tank
Roc City Manx tank.
Clubman bars
DCC indexable rearsets.
Custom exhaust header.

To come will be:
80mm cylinder bore to make 284cc
36mm Mikuni Flatslide carb.
Web Cam TT250 88mc Grind
Dual Valve springs and titanium retainers

Down the road somewhere:
Decent set of rear shocks.

I plan on doing a decent paint job as well and I have been considering swapping to a smaller front sprocket just to bring the torque back up a bit more.

Hi Brodie, Looking forward to seeing how the bike turns out in Café mode. I had same idle problems as you. I found that one jet up on the pilot, two up on the main and one notch down on the needle circlip work out great. I also had to re-seal my intake boot as it had cracked with age - very common apparently.

Plenty of pics please.

Thanks Steve, I went up 1 on all three jets the other week and it is awesome. Idle problems are gone and the power is a lot better. Last week I changed the clutch and she is a different bike all together.
I am planning on a different carby as I am still not a fan of the Mikuni BS series. As many people have put it "CV carbs are a PITA to tune right" I have not tried as once I install the 284 cylinder I am going to need a lot more air flow which the stock carb just won't do with out a bit of work.

I have been looking at getting an 80mm XS650 piston which has the right pin size and looks like the valves should clear. it all depends on how much I can take out of the original sleeve. 80mm is pushing it quite far. The sleeve I have measures 81.7mm which should leave enough of a wall. I will be going out tomorrow to inquire about just how much can be removed from the inside.

Also I have just ordered a set of clubmans for my bike which should drastically change the stance. I have been looking at ways to fit rearsets on but I am thinking I will need to weld in some gussets for a decent mount point.

I have a 200 tank on mine actually. Good luck with the build

Shawzie said:

I have a 200 tank on mine actually. Good luck with the build

Click to expand...

Thanks mate, Got any pictures laying around to share?

Just got back from the engineering shop, my 284cc dream has been crushed by budget haha. After talking with the blokes for a while and discussing my plans he recommended the maximum without a reseelve to be 76.5mm leaving me with 2.5mm sleeve wall. I had a chat and asked about 1.5mm wall but he said it would not be enough and he would rather I had a 3mm. So the new plan is 76.5mm bore which will make 260cc. Doesn't sound like much but considering that the SR "250" is really a 239cc engine a jump of 21cc is enough to move me along a little better. Now that cam is looking even more enticing.

Anyway I figured I would make a list of sizes with pistons to help any one else planning on doing the same thing out. This is just the sizes with pistons that I have found, feel free to add info it you know of any other combos.

BIG BORE SR250 Sizes with case bore and resleeve

These use a '89 YMF350 bigbear piston, Wiseco part # are 4419M08300 for 83 and 4419M08400 for 84
84mm=312.2cc
83mm=305.7cc

These use a '81 XS650 Big Bore piston, Wiseco part # are 8635P80 for 80 and 8635P81 for 81
81mm=291.2cc
80mm=284cc

Big Bore SR250 Without case bore or resleeve
76.5mm=259.7cc this is the biggest that I have been told is safe but I can't find a piston for it.

After a ton of research I have found that GS1150 pistons have the right pin. Wiseco part # are 4345M07600 for 76 and 4345M07700 for 77.
77mm=263.1cc
76mm=256.3cc

These look to be the go for big bore without reseelve. I am going to go back to the engineers tomorrow and ask them what they think of 77mm bore. After that it is only a matter of finding a headgasket to suit.

Ohh yeah and I ordered a set of clubman bars from Mostyn Industries http://mostynindustries.com.au/
And a nice new seat from Sean at Roc City Cafe Racers. http://www.roccitycafe.com
All that I need now is some rearsets and that damn cb200 tank lol. Then a hell of a lot of fab work.

Not yet but I am working on it

Have you thought of just getting an xt250 or a tt250 cylinder, at the 4th over bore (40 thou or 1mm). That should be 76mm, not quite there but closer. But everything should still line up from what I've been told.

Just a thought

Yeah thought about that. Also have been adding up the costs and thinking about what needs to be done and what doesn't.

After a bit of consideration and a new project sort of falling in my lap I have decided to sell the SR, it has served me well but in my search for speed I came across am '83 GS750 16valve for a carton of beer.
Watch for that build soon, I pick it up tomorrow. For now thought the SR will be getting a K&N filter and a few bits fixed up then it will be on the market as I ride it and fix the GS.

The reason that I have decided to start a new build is because by the time I spend around $800 getting the engine in the SR to the stage I want I could have spent that on a larger bike getting it rideable.
So once I see what condition the GS is in I will be able to go from there. For now though I need to get out and get some "Finished" pics of the SR, more like "project abandoned" really though. As much as I like this bike I feel it will never serve me any more than what it is, a city commuter. Now if I was a few inches shorter and a few pounds lighter it might be better but at 6 foot 1 I think I have out grown this bike fairly fast (coming from the guy with a stack of Z50s). Sorry to disappoint anyone that wanted to see it done. I can tell you after the research I have done, unless you are going to get the case bored a big bore is not really worth it for a SR. My advice, stick a BW350 engine in!

Its a bit of a shame to see it fall by the wayside. But you've come to similar conclusions I have with my SR.

I'm gunna stick with mine for now and try a few things with it. Maybe I should start taking some photos and start a build thread as well. Mainly because for me this a learning bike, seeing what seems to work and what doesn't and most importantly what things should cost. Also because I have a Z650 ready for some attention when I have my skills and confidence up a bit.

Look forward to seeing what you do with the GS.

Thanks mate. Yeah I do feel bad but I am keeping the SR for a while. Need something to ride whilst I work on the GS.