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Project GSF250P Slingshot rework...

Discussion in 'Your 250cc Projects' started by Bab, Oct 13, 2017.

  1. Murdo

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

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  2. Bab

    Bab Well-Known Member

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    Exactly!! I'm relieved to know I'm not the only one thinking that way.
    I took the bike off the rack this morning and took it for a spin around the block. It starts first poke of the switch with about 1/2 choke. Acceleration has a hesitation around 4,000 rpm, but then goes like snot! A residential zone, schools and all, isn't the optimum location to cut it loose. I did get it out this afternoon and opened it up to 130 km/hr. Seemed to run good, but still a slight hesitation when you roll it on. Letting off the throttle it seems to idle down and settle out, however I did up the idle to just below 2,000 to accommodate my insecurities. The clutch needs adjustment because just getting ready to release the handle is enough to get rolling.
    There are some noises I'm hearing, and am not sure what they may be. This part of the rebuild will include some trial & error because it has been ~17 - 18 years since I was on a chain driven bike. The last 4 years were on the shaft driven NT, and 14 years prior was a belt driven Ultraglide. I do know the chain needs tightened, alignment will be checked at the same time, but the noise I'm zoning in on is in the drive train. It's not apparent when the bike is idling or reving in neutral, or in gear with the clutch in. It is not alarming, but is noticeable when I'm idling down, gearing down for a stop or creep.
    This bike has taken me by surprise. That weight:horsepower ratio has put a serious grin on this mug. There is going to be a learning curve ahead because the last 250 I owned was in the 60's and was a HD (Amerachi) Sprint, one lunger. Sure wish I had it to-day $$$$$$$.
     
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  3. Bab

    Bab Well-Known Member

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    I put the bike back on the cradle and am now changing out the fluids. I have an oil filter and O-ring in transit (should have bought everything earlier, but wouldn't admit to myself it was going to happen regardless of what we found in the engine). So at this point the brakes have been flushed, and the rad and reservoir was emptied, flushed with clean water, and new coolant installed. One more session of burping the rad to ensure all the air is out and we're good there.
    Using the adjusters on the ends of the clutch cable, I have achieved more range of movement of the clutch leaver to the point I now will be able to control where the clutch disengages in a more controlled manner.
    This leads me to asking a question about the clutch that likely applies to other bikes as well. I'm familiar with large industrial clutches and brakes, and the importance of maintaining the "air gap". The air gap is the combined clearance between the friction plates, and the clutch or wear plates that occurs when the clutch is disengaged, allowing the components to rotate with no torque being applied to the shaft. The efficiency of the clutch, and response time when engaged will be directly effected by the amount of the air gap initially set when the clutch is new. As the linings / friction material and the clutch /wear plates deteriorate from use the gap is kept to a minimum by adjustments, or the removal of shims.
    On the bike we make adjustments for wear at the cable ends, but what about the initial set up of a new or completely disassembled unit. I'm aware of the rotational force caused by the cable translating into the transverse movement of the throw rod resulting in pushing the pressure plate. This causes the opening of the air gap and the disengagement of the clutch. Is there further adjustments at the cable end of the throw rod
    that needs attention, and if so how is it measured, or regulated? Is there specific dimensions of the combined clutch stack given in the repair manuals? With out the manuals can we extrapolate these dimensions by measuring the basket, or do we have blind faith in purchasing the clutch packs from vendors who we hope have scruples, as well as knowledge about what they are selling? ...Bab

    IMG_20171208_095453.jpg
     
  4. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Different manufacturers have different methods but most will have some adjustment on the Clutch push rod mainly to take up any manufacturing tolerances etc...and you can during the life of the clutch (if you need to ) adjust that pushrod to give you a bit more adjustment on the cable ends but you should have sufficient adjustment over the life of a clutch pack with a new cable...
    Friction plates and driven plates all have a max and min thickness as does the basket so these can be measured during the life of the clutch for wear.. as can the free length of the springs.
    As we mostly talk about "wet" clutches with regard to 250cc bikes the oil we use also has an effect on the clutch.. but in general, yes, we put a hell of a lot of faith in the OEM's and aftermarket vendors that the clutch packs they sell are to manufacturers specifications.
    I am not so sure some of the vendors have too much knowledge about what they are selling but there are good ones out there as well as plenty of combined knowledge on what does and doesn't work in this community...
     
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  5. Bab

    Bab Well-Known Member

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    Your mention of the wet clutch, Andych, has me wondering how many bike owners have gotten into trouble by using oil with friction modifiers, thinking they are saving their motor. With so many choices of oils available we need to make sure labels are carefully read and understood. Choosing oil would be a little easier if the print was a tad larger too...

    I had the Slingshot running the other day and was attempting to tweak the carbs by changing the air mixture screws. I had 3 that were free, but one was frozen in place. I obviously missed cleaning it when I had the carbs on the bench. They're back on the bench again. The slot in the head of the screw was pooched, and I dicked around grinding screwdrivers in an attempt to loosen it to no avail. I tried soaking it with screw loose of all different makes and varieties ( from top and bottom), tried light impacts while under torque, tried some heat. I'm to the point I may end up drilling it out. What else should I try before I risk compromising the carb with my drill? I'm open and grateful for any suggestions...Bab
     
  6. Wozza

    Wozza Active Member

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    heat it some more...think the brass will expand faster than the alloy, so more heat in the carb body,if you have some solder(not sodder :D ) flux try wicking that in with heat...failing that drill a small hole on and edge of the screw and use a small drift and decent hammer...
     
  7. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Fuel screw on the Mikuni as it's on the head side, air screw would be on the filter side of the carby

    Could try heating up the carb body a little and using some candle wax to get in between the mixture screw and carb body
    Drilling it out may cause it to tighten it more, unless you use a l/h drill bit
     
  8. Murdo

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

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    I would suggest the heat and soldering flux too.
    If you do get to the point of drilling out be sure to only use a left hand twist drill bit as it will probably grab in the brass and spin it out.
     
  9. Bab

    Bab Well-Known Member

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    Thanks all!

    In the past I've had good luck with heat and "Liquid Wrench" which is a penetrating type oil with graphite. This time it let me down. I can't use the ***** punch method because the screw is too deep in the barrel it screws into. I never thought of the wax idea and have seen it used on U-Tube (when you have a brain fart, at least it doesn't stink). I have not heard of using the (sodden) flux and will give it a try. I'll let you know how I make out later.

    In the future what do I do to eliminate this from happening? I learned to put oil on threads before assembly as a kid working on bicycles, then later in life I discovered Anti-seize, and I haven't set the can of it down since. Does any one treat the screw threads with anything before the installation?
     
  10. Murdo

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

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    Brass and alloy are not the best of friends chemically and to help I use rubber grease (the red one) or silicone grease when assembling carb screws.
     
  11. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    I put Inox on everything

    inox.jpg


    And rubber grease on o rings and carb boots etc


    rubber grease sml.jpg
     
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  12. Bab

    Bab Well-Known Member

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    I went back at the air mixture screw with the previous suggestions, but failed miserably. The slot in the screw was sketchy before I had a hand in it, and now it's totally mauled. I ended up using a rotary tool to cut slots down the barrel and fashioned a new slot in the head of the screw. This gave me a purchase on the screw, and with heat and cold and various assortments of penetrating oils, and flux The screw actually moved. Eventually I worked it out. Moisture and perhaps galvanic corrosion was evedent in the threads. I polished up the head of the screw, cleaned and defined the slot and cleaned out he threads. With all the burrs removed created by cutting the outer portion, the lubricated screw was easily turned into position. There is still lots of thread in the "barrel" to allow adjustment of the screw without exposing the business end of it to the slots I created. The screw now functions like its brothers.

    I feel bad about ravaging the carb bowel as I did, because I have been critical about savage methods others use on equipment instead of using some skill and finesse. This procedure was a compromise on my part as I was not prepared to purchase carb parts at this time. Anyways the boots were greased up, the carbs reinstalled with 4 working air mix screws, and one scarred fuel bowel. Today the tank goes on, and we can tinker again.
     
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  13. Bab

    Bab Well-Known Member

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    My last notes had me waiting for an oil filter to arrive. My intention was to fire up the bike and attempt to bring the carbs into some sort of harmony by ear. With that done, and the oil warm I'd drop it and change the filter and oil. I'm still waiting for the filter. It's circling the globe somewhere, and my friends in Russia are telling me it is because of a busy Christmas season. Apparently they are still celebrating because the filter was ordered 7 Dec. and I've still not received it. The tracking indicates it has been forwarded to the "correct" address 3 times now, so they must be hung over from the celebrations. More to come on this one...

    Going back to the frozen (still winter here) carb adjust screw I thought I'd attempt to illustrate what I did to access it in order to form a slot so I could work it out.

    IMG_20180123_115242.jpg IMG_20180123_115326.jpg IMG_20180123_115510.jpg

    Obviously I should have taken the photos while everything was still on the bench.

    Meanwhile back at the bench I have taken the faulty ignition module and removed the transistors, and capacitors in preparation for sourcing out replacements.

    IMG_20180122_105834.jpg IMG_20180123_113637.jpg IMG_20180123_114634.jpg

    That was the easy part. I now have to find the replacements, but have failed miserably. The capacitors won't be a problem, but the transistors have me stumped at the present. I have searched for hours for Darlington transistors with numbers D1976 2 H4 but can't find anything of the sort.

    IMG_20180124_164011.jpg IMG_20180124_170858.jpg

    I have drawn an enlarged facsimile with the hope someone might recognise the trade mark of the manufacturer, or perhaps translate what the numbers mean so I might be able to find an equivalent substitute. I've not attempted this type of repairs prior to this and I'm curious as to the costs of the potential repair, and will it be worth the effort?
     
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  14. Wozza

    Wozza Active Member

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  15. Bab

    Bab Well-Known Member

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    Thanks Wozza, you and My67xr have given me a leg up in the hunt. I'll be back to you with results.
     
  16. Bab

    Bab Well-Known Member

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    Wazza! You just woke me up to My67xr's instruction previously posted to add "2S" as a prefix to the part number when searching for it. I'm thick as two planks at times...
     
  17. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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  18. Bab

    Bab Well-Known Member

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    You guys are top drawer! The transistors are on their way! Heading to local shop tomorrow for the capacitors. Thanks again...
     
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  19. Bab

    Bab Well-Known Member

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    Greetings to all...
    Life has a way of distracting us from things we would rather be doing, to focusing on the things we need to do. Anyway I'm back working on the Slingshot / Bandit.

    The bike sat all winter, and so bought a battery and dropped it in, set the fuel cock to prime, choked it and it started on the 4th attempt. However it would not idle with the choke off, and the idle adjustment has no influence on the revs. I fear I have overlooked something when fitting the carbs and airbox. I'll be checking things out in that direction soon.

    Once the bike warmed up I dropped the oil out of it and noticed the consistency was quite thin, and I suspect by the smell was contaminated by fuel. This was no surprise to me because I was aware the bike sat idle for an unknown length of time prior to me getting my hands on it. The filter and gasket change was uneventful, although it was the first time for me to change a cartridge style filter.

    I haven't had much to contribute to the forum lately, but in reading some of the questions put to the members here by other owners of the 250 Bandit, I will assure you the plugs can come out of the '93 with out taking the tank off. The filter can be changed with out messing with the exhaust. My workshop is modest, with no exotic tools with the exception of JIS screwdrivers. My tool box holds the basic sockets, wrenches, and screwdrivers, inexpensive verniers, and micrometers. My approach to getting the job done includes unorthodox ways to use what I have on hand, and if needed to modify tools, or material to suit the occasion. I've said it before, take time to sit and think the process through so you don't make more work for yourself. It's not a race, its a challenge that when done will either reward you with success, or hard earned experience that can be applied in the future. Regards...
     
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  20. Mike Fulcher

    Mike Fulcher Active Member

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    Just going back to the problem you had with replacing your fork leg seals, I had the same problem with my Yam 250 SRX.
    It failed a WOF ( if you can understand Kiwi English) because of leaking seals.
    I could not remove either of those darned (once again Kiwi slang)fork leg screws, so what I did was to remove one fork leg at a time, & modified quite a reasonably sized screwdriver to be driven between the inner fork leg & the seal, being careful not to damage the inner leg, & removed the old seal that way. Chrome is a very hard surface & by doing it carefully this way it was a piece of piss (another Kiwi slang) enjoying your repituire sorry couldn't spell that one & spell check was no help, I mean conversation.
     
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