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Project Bens GSX250 Cafe Project

Discussion in 'Your 250cc Projects' started by Ben Mulligan, Nov 14, 2013.

  1. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Don't think it sounds any 'rattlier' than normal. Remember it is an air cooled engine with lots of 'noise enhanchers' (fins) surrounding it.
    Your carbs seem ok too.
     
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  2. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    So my carburettor boots disintegrated the other day. I've jsut replaced them and the bike seems to be bogging down around 5000-7000 RPM. I clipped the needles from top position to position 3 (total of 5) and it got worse, so it must be too rich.

    If I'm at needle clip position 1 (Top) of 5, and its still bogging down in the mid (5k-7k RPM) than should I buy a longer needle or change the needle emulsion tube?
     
  3. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Are you certain there are no air leaks?
     
  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    In the last section few pages of the carburation chapter in of Four-Stroke Performance Tuning

    by A Graham Bell
    There is some useful information on choosing needle and needle jet (emulsion tube)
    You cannot use a longer needle. You change the diameter and taper of the needle to alter the mixture.

    To match those rpm values to slide position might be a good first step. Mark your accelerator with some temporary system so you can determine at what fraction of full throttle you are experiencing the problems e.g. 1/2 to 3/4 etc. Then you can keep a journal as you try different settings.

    I have sent you a pm with some useful details.
    cheers
    Blair
     
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  5. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Thanks mate this will really help!
     
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  6. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    So I recently got out on the road. Knocked out 150 km's even with the slight flat spot. Bike ran well and true on the road.

    Recently, I took the side cover off to change the clutch plates. Put the covers back on and fiulled it back up with fresh oil (2.4L roughly) Bike starts and runs, rides for a couple of minutes and after it warms up It starts to burble and pop and sounds like its only on one cylinder. Bike dies and needs a couple of minutes to start again. I took the spark plugs out and put new iridium ones in, and I'm getting a faint orange spark out of both of them.

    I've checked the timing marks are in the correct positions on the signal generator. I've also replaced one coil pack lead and plug so that it wasnt the resistance of the cable. All to no avail.

    Bike warms up, runs and after 5 minutes drops a cylinder and dies.

    I'd love any ideas?
     
  7. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Do you still have spark when it stops?
     
  8. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Faint orange sounds like crap spark to me

    Should be blue/purple as far as I know
     
  9. Clancy1

    Clancy1 Well-Known Member

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    check the resistance of your coils, however generally if a coil drops, it does it pretty suddenly and doesn't come and go etc.
    could be the condensors in the ignition set.
    Couple of things to try there.
    Try cleaning up your ATU gear (behind the little suzuki cover on the right side of the engine
    But first I'd be checking the resistance across both phases of the coils, can't remember exactly but one will be about 4/5 ohms and the other willbe around 19,000-28,000ohms
    Check your manual for how to do it etc


    Good luck
     
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  10. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Hi Guys, due for an update.

    After messing around with that engine for so long now, I took the rocker cover off again and the timing wasn't aligned properly. It is obviously and obstruction in the engine (chain guides or something) and mixed with some oil leaks, a few stripped bolts etc etc I decided to pull out that engine. So I did

    I went down to the wrecker I got the cam chain tensioner off and he sold me an 1985 engine in factory black wth less KM's on it for $400. I dropped it in the bike and it wouldn't fire! After giving the pickups an inspection turns out the 85 used a newer pickup style so I changed them out for the old ones and away she went. This engine is quieter, timing is perfect, gear changes are nicer, exhaust fits better, its black (like i wanted) and it goes just as well (realistically)

    Carbies were balanced with a vacuum balancer and the flat spot still existed around 8k RPM and the transition from Pilot jet to main jet was a little slow. I dropped the needle from top position to fourth position each time taking it for a squirt and the power got better, and better, and better. The flat spot still exists but I don't want to change the main jet because she screams along at the top end once shes on mains. I figure this is the problem with no airbox the mixture at that point just can't be right without starving a little more air and there is no practical way to do that.

    So I now have a GSX 250 Engine sitting at home minus pickups + tensioner + starter, with worked heads and new rings and peeling paint. At least I have some spare Cams/chain/gears/covers/valves/springs etc. etc.

    I guess something had to give. I'm happy she rides around now.

    IMG_5442.jpg IMG_5444.jpg IMG_5445.jpg IMG_5448.jpg IMG_5453.jpg IMG_5559.jpg
     
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  11. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Turns out that moving the Main jet up 1 size to 125 from 120 fixed the flat spot, sacrificed top end power but made the mid more rideable.

    Main:125 (stock 117.5)
    Pilot: 17.5 (stock)
    Needle: 5DFT76 (Middle position - stock)
    Pilot screws 1 1/2 Turns (stock)
    Idle screw 1/2 turn in

    Runs like a dream now.... it was so simple all along.
     
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  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Your build has to be the most unsimple ever :lolsign:

    Glad to hear its running ! :thumb_ups:
     
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  13. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    This project is for sale if anyone is interested. I've run out of time and money and some other more pressing things have taken priority. Currently bike IS NOT running due to unseen electrical fault. It was making spark with new igniter and pickups only a few days ago, now its just eating fuses.

    1981 Suzuki GSX250 (with newer 1985 engine)
    Custom paint and fibreglass seat
    Rear hoop welded on and battery up under hump
    Low profiles Chrome Speedo’s with LED warning lights
    Clip ons with POSH switches
    Centre Mounted Key Block
    Billet aluminium rear sets
    2-1 Exhaust (needs respray) from Japan
    Carbs tuned and ready to go
    2x Batteries

    Spares:
    1981 Engine - Heads worked on by mechanic, new rings and timing chain, valves lapped and spring tensions done. Polished side covers. New clutch pads and springs. Engine slips timing, best as for parts or to swap worked heads to second engine)
    1981 Pickups and Igniter (unsure about igniters operation)
    1981 Cam Chain Tensioner with spare seals

    PM me if interested or email me ben@benmulligan.com
     
  14. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    I'm not sure whether to be sad or happy for you. As Grey said, your build has been the most "unsimple" ever. Hopefully you'll find a buyer soon and move on. Hope all is well Ben.

    Cheers

    Frank
     
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  15. Phil

    Phil Senior Member Contributing Member

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    Sad day indeed.....your build has kept me intrigued on so many levels.
    I've admired your tenacity to never give up.....god knowns many others would have.
    In view of your decision to sell your bike, trust you get a quick sale and are able to move on.
    Good luck mate.
     
  16. RDickens

    RDickens Active Member

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    Hello, just picked back up on this thread. I have been working pretty hard lately on getting my bike (83 GSX250) done. I have been looking at adding rear sets lately. I was wondering if you could show how you mounted them. I know my bike is set up just a bit different to yours. Can the brake side be mounted to the old brake arm pivot? Also, where did you mount
     
  17. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    Hey Mate, I had the welder cut some plate steel 6-7mm and weld it on in the shape for my rear sets. Mine had to be mounted wit ha screw i nthe back so it was a little different setup. I found it had to fond a set that mounted to the original position and was the right distance back for my clip ons to be comfortable.

    The gear shifter had to be made of all thread and had a pivoting brass knuckle on it and the brake lever had to have a returns spring on it to be legal, so it was a lot of work. I'd say take it to someone whos done it before if you are unsure
     
  18. RDickens

    RDickens Active Member

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    Thanks for the info Ben. After looking at it. I think I can remove the bit the old brake pedal mounted too. make a slug that I can attach the old brake linkage to the rear set. I will just have to make up a mount to match the shift side. I think I may be able to make it work.

    Also, I noticed on the pictures of your motor, it appears you replaced all the engine cover bolts. Your's appear black. If you did, where did you fined replacements?
     
  19. Ben Mulligan

    Ben Mulligan Well-Known Member Premium Member Contributing Member

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    I found replacements at a bike bolts shop on ebay. They were aluminium, however a lot of mechanics I spoke to said even for engine cover bolts not to use aluminium, in terms of longevity they may seize in with the steel? Something like that. I think tensile strength is a problem. They were much easier to use with the hex/alan key thing
     
  20. RDickens

    RDickens Active Member

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    Was this at a local bike bolt shop? Or someplace online?
     

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