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Drag Racing 1978 Suzuki TS185 Nostalgia Bike

Discussion in 'Motorcycle Racing and Track Days' started by Frankster, Mar 22, 2020.

  1. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    This guy does a reasonable job of explaining pipe length to tuned RPM range- I actually think my initial crazy idea of turning it around will work for you to get an almost straight pipe which will be easy to tune



    Another thing to know is that the steepness of the cones, divergent and convergent narrows the powerband range and can make it come on really strong - I recall seeing some Honda 500GP pipes that were so steep the only thing I word think of was Savage, which by all accounts it was.

    First cone scavenges the cylinder and the second cone pushes the escaped fresh fuel charge back in at the right time

    For comparison look at say the DT250 - very shallow divergent and convergent cones and a thin belly and almost no powerband because you don't want farmers flipping them and ending up in cow dung
     
  3. Murdo

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

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    The frame is all Standard Suzuki and wheels. Nothing has been changed angle wise from when it was a trail bike. The off set to the shock is to clear the chain. The chain 'flapping' around that much could be the vibration you were feeling. Don't know why it would do that as it was new chain and sprockets when I built it.
    They are standard Suzuki forks and wheels. The steering head bearings might need changing to tapered rollers, but I think replacing the 30yr old tyre might help.
    It is Loctite grey maxx sealant, same as case sealant on the exhaust. If you don't want to use it or similar then put an O ring on the end of the pipe and hope it doesn't leak.
    I changed the mid section of the pipe to gain more mid range torque as I remember it had a big flat spot in the power, maybe I put too much in and may need to shorten it an bit. Do the calculations first before cutting it as it may need to be even longer.
    Don't go dicking around with head gaskets until the pipe is sorted, it will just confuse the issue. If you can find a YZ pipe and fit it through the frame to try.
    I am sorry that the weekend didn't work out as planned, I tried to have it all as you wanted but the best laid plans, etc.
     
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  4. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    @Murdo would the lack of an airbox be causing that issue with the midrange prior to lengthening the pipe?
     
  5. Frankster

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

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    Morning everyone.

    @ruckusman if we turn the cylinder around, will the carb have issues with air being forced into it? I'd like to get it to run right in normal configuration and then experiment later. I'm leaning towards an airbox too, just to eliminate another possible issue. I guess the carb is sucking in hot air at some stage of the run and the amount of air swirl might also be an issue. The current filter gives the bike a classic (other than it is green) look, but might not be helping with the tune. 34HP @ 8K would be just fine thanks.

    @Murdo no dicking around here bud. I'm so much of a novice that I'm just doing what you and anyone else I trust tells me. I didn't realise you had a mid-range flat spot. In my opinion the engine still has one. The "interruption" I mentioned could also be described as a flat spot. I never really got that sorted due to other issues we were experiencing and not wanting to pin the throttle through the flat spot on an engine that I was missing gear changes on. Someone mentioned rubberising the engine mounts to stop it breaking bolts and reduce the vibration through the frame. Thoughts? I was also thinking of reinforcing the frame under the engine where the stone guard would normally be. The head stem bearings are notchy as soon as you do them up. Is that because I'm doing them up too tight?

    @my67xr that website is where I got the '81 YZ250 manual from. He's a great web resource.

    @GreyImport thanks for confirming that.

    @jmw76 there's not much room in the rear and about 20mm to play with up front. I was going to turn the triple tree around to give me the same rake, but increase the trail. I've already tested it and there's plenty of room to do it and the head stops give me about 15-20 degrees of turn angle. Enough to test it up the street before the cops come around.

    Thanks for everyone's input. Once I get new tyres on the thing, I'll take it a drag strip (if any are still in business) and do some testing. Next job is to pull apart the front forks and see what's going on in there.
     
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Agreed on turning the cylinder - it was just a suggestion as I've done reading recently where guys that drag race seriously hopped up Banshee 350 (RZ) motors do that and the straight pipe out the back is good for some ponies - that would of course be contingent on you having dimensions for a stock pipe or something which is known to work

    I was thinking more along the lines it would be easier for you to actually make a pipe which is straight and I think that the carb inlet rubber gets inverted to return it to level

    One good thing is that these old bikes are popular so info on stock pipe dimension will be available, then to compare those with what you have and work from there
     
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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK so I just got around to reading that post from your first outing and a new plug got you revving past 5K rpm up to 6.5K RPM - just putting this out there, what about old components in the CDI module as the original problem was ignition related - would they be 45 years old, or older?

    Capacitors age, easy replacement

    I think the lengthened belly of the pipe will have lowered the resonance, perhaps that is the 6.5K RPM you managed where it's resonating properly.
     
  8. Frankster

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

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    The new plug actually let me go higher than 6,500rpm but I was experiencing a major flat spot, so I was changing gears at that point. I think I revved it out when returning to the pit area and it got up to 8,000rpm. And, that was the only time I actually felt the engine "pull". But, I do agree that I need to go over all aspects of the engine electrics to confirm it is running right. It was difficult for Murdo to do any real work other than jetting while we were at the drags. My highest priority is to get the bike stable. Once I have confidence that it won't try to throw me, then I will get after it. I don't want to blow it up, so I have plenty of reading and learning ahead of me. If I could eventually get 40hp out of it, I would be over the moon. I've stopped reading about squish and other performance mods, while I try and sort out the death wobbles. Keep coming with the ideas Ruckus. They all help. Cheer Frank
     
  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I think the tapered rollers will get that sorted, if it doesn't then check your verticals/horizontals for the front end, unlikely but still possible.

    This is a great read on the YZ250's of that era and there were port changes on those models to tame things between years

    Shame the pics are missing

    http://pulpmx.com/2015/06/24/gps-classic-steel-105-75-yz250b/

    I remember my IT465 was good for 140 at least - where the speedo ran out plus it had +3 on the front @14 teeth - I tried it with the stock 11 on the front one day and all it did was try to emulate a unicycle and I couldn't sit any further up the tank, definitely not sensible on the roads in peak hour

    Knowing Murdo the way we do, I reckon that pipe will be very close to stock or something very functional and pipes are detrimentally off-resonance right before they come into resonance

    Check the CDI if possible and replace the capacitors
     
  10. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Another couple of idea's for sorting the tank slapping,
    seeing the rub mark on the rear chain guide's the wobbles, could be coming from the rear ?
    Check the spoke tension on front and rear wheel's, and check the rear swingarm bush's for wear
     
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  11. Frankster

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

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    @my67xr Funny you should mention the wobbles might be coming from the rear...on at least one occasion I did mention to Murdo and Pete that it felt like the shake started from the rear wheel and moved through the frame to the front! Not on each occasion, but definitely felt like that on a couple of runs. I may be dealing with a couple of issues affecting stability.

    @ruckusman any suggestions where I can get tapered bearings for the forks? I've never changed a bike from ball to taper before, so may need some help when I get around to it. I'm reading about expansion chambers for WOT applications (drag racing) and it would seem a straight through pipe is often used. The curved pipes seem to be more about avoiding them getting hit and dented.
     
  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Tapered rollers are used in all sorts of applications, you'll need the tube diameter of the triple, top and bottom to start, then the tube diameter of the frame for the second diameter - from there it would likely be a simple walk in at the local bearing shop hopefully if they are common sizes.

    The bonus of a straight pipe is that obviously the gases flow a straight path and the lack of all of the meandering winds allow the pules to work at their optimum - there's one more potential advantage and that is to make a slippy pipe which was employed by karters which mostly run WOT or close to it most of the time - it's a sliding section of the end of the belly and divergent cone which slides forwards to lower the volume and raise the rev range of the resonance.

    Exhaust valves have nowadays done away with most of the need for anything that exotic - I would put that into a well if I had unlimited time and funds category, but the reverse cylinder is definitely doable and perhaps not as much work and fiddling as it sounds - remember Yamaha did it with one of their TZR's - they ended up having to have all sorts of other intricacies like coolant flow past the carbs to prevent icing - your application is much more straight forward (AHEM backwards) pardon the pun
     
  14. Frankster

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

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    Ordered some through Pablo's Tyres.
     
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  15. Murdo

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

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    The reverse cylinder would be an overwhelming amount of work for not a great gain. The transfers and inlet on these old Yamaha's are well embedded into the case mouth and would require heaps of welding and milling to line up with a reverse barrel.
    The bike runs a points magneto, no cdi.
    The bolt that broke runs through a rubber engine mount. I would run an 8mm drill through the frame mounts and the rubber bush to be sure that they are aligned correctly, then put in a new 8mm high tensile bolt.
    I have never had any trouble running the open foam filter on earlier two strokes, but building a still air box would probably be a good step.
    Don't know that putting a welded plate on the bottom of the frame would make any difference, might.
    Wouldn't suggest turning the fork clamps backwards as a good idea.
    Check the chain on a flat piece of board to make sure it is running straight. It may be the cause of the bad vibes.
     
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  16. Frankster

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

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    The bolt that broke runs through a rubber engine mount. I would run an 8mm drill through the frame mounts and the rubber bush to be sure that they are aligned correctly, then put in a new 8mm high tensile bolt. Will do

    I have never had any trouble running the open foam filter on earlier two strokes, but building a still air box would probably be a good step. Maybe later

    Don't know that putting a welded plate on the bottom of the frame would make any difference, might. Can't hurt, right?

    Wouldn't suggest turning the fork clamps backwards as a good idea. Why not?

    Check the chain on a flat piece of board to make sure it is running straight. It may be the cause of the bad vibes. Are you saying lay the chain on its side or break the chain and laying it out longways?
     
  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Forgot about the transfers if they don't match up. Bummer

    With points/magneto does that mean it's static timed?

    Been decades since I dealt with that - I do recall struggling dealing with an IT175 which stubbornly ran backwards because someone had put another coil plate in it from something else - its started fine, just never ran forwards.

    I had a 40 year old McCulloch chainsaw that liked to consume the condensor (capacitors) connected to the points and run like crap - possible cause?
     
  18. Murdo

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

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    Turning the fork clamps (tripple tree to the Americans (how do you get the tripple bit from two clamps) watching) around will give you almost zero caster (trail to our USA friends) and be very nervous to steer.
    Open the master link and lay flat on a board then look along to see if there is any twist to the links. Lay a straight piece of square tube beside and get down at eye level and look that way too.
    Points are static timed. If you wish to go cdi there is a cdi flywheel in the cardboard box but you will need to get the back plate and coils from a 'D' or 'E' model DT250.
    Condenser could be a problem, but was new when fitted. Disconnect and test.
     
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  19. Frankster

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

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    Turning the fork clamps around will give you almost zero caster (trail to our USA friends) and be very nervous to steer. Not that I'm going to do it, but are we talking about different things?

    Reversing the triple tree keeps the same rake & offset, but increases trail because you've moved the centre axle further back. Doing this obviously shortens the wheelbase (is that what you meant about it being nervous to steer?).

    TrailRakeOffset.JPG

    Great read if you're interested in steering geometry and other magical things. https://motochassis.com/articles/experiments-with-steering-geometry/

    Points are static timed. If you wish to go cdi there is a cdi flywheel in the cardboard box but you will need to get the back plate and coils from a 'D' or 'E' model DT250. Anyone know where I can get these items. I'd like to do this mode as I am shite scared of points.

    Condenser could be a problem, but was new when fitted. Disconnect and test. Pretend I don't know what you're talking about...what exactly am I testing for and how would I be testing the condenser?
     
    Last edited: Mar 23, 2020
  20. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Condenser will looks like this or very similar and be attached to the points- my very very old Subaru used to like to eat them and stop running whenever I visited my Mum for some strange reason - so I resorted to keeping spares on hand at all times

    But that's an outside chance because usually a defunct condenser means it won't run at all

    Worth checking the points gap and I used to have a multimeter which had dwell time which is the more useful measurement

    Points just need to be gapped, nothing to fear, think of it like the whole float height fuel level measurement

    When they are gapped correctly, the dwell time should be appropriate

    [​IMG]
     
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    Last edited: Mar 23, 2020
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