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Thread: R90S starting problem

  1. #1
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    R90S starting problem

    Hi Guys,

    I have a great 74 R90S which runs really well at all RPM, but is really hard to get going especially when the weather is cold. The bike is dual plugged and the timing is set almost to the OT mark. Valves are set.

    Thanks to a really good battery, I almost warm the bike up with the starter and then the bike well half run with the starter still engaged and finally will start, sometimes after numerous sputters and dieing.

    I've had a few airheads, but this is my first S with the Del Otros.

    Two things. 1. The choke lever seems to be over choking when the lever is fully depressed. 2. I noticed the right side carb rotates easily on the intake tube. Perhaps a vacuum leak here?

    The bike was dual plugged oh, 30 years ago but only has 50K on the clock. Perhaps weak spark?

    PD

  2. #2
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    PD -

    Sounds like you have a cold start issue since it seems to run fine when warmed up. You might want to check the coil connections where the high tension lead plugs in to the coil tower...could be some corrosion in there.

    I'm not that familiar with the Dell's...could be you're flooding the engine. You might want to try altering your starting routine to reduce the choking. Yeah, the hose clamps holding the carbs should be tight. Easy to fix that.

    As for dual plugging, I've read a lot of discussion about how to route the spark plug wires...which coil does the top plugs, the other the bottom plugs; or maybe one coil does one side, the other coil the other side. I've never really paid that much attention, but this latter approach doesn't seem like a good idea...if a coil fails, you're kind of in trouble...until you reroute your wires.

    If you have a marginal tune up, the spark plugs are old, the spark plug wires are old, there's corrosion in the coils...all of these things tap energy off and make a marginal system hard to start. So be sure all parts are in the best shape they can be.

    Also, be sure you're getting enough fuel in the float bowl...too low of a level will make it hard for the carb to suck up the gas to run.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
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  3. #3
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    I had problems because one of my carbs wasn't tightly clamped on the cylinder side. Start there.
    61 Gold Star, 76 R90S, 03 CBR600RR, '13 690 Duke, '14 Street Triple R

  4. #4
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    Thanks for the input

    Thanks for the replies. All good thoughts. Yes, since the dual plugging/ignition set up is so old, I am thinking this could be the main cause. I did not notice the loose air intake tube until I accidentally bumped the carb while connecting the trickle charger.

    Like most of us, I have delt with quite a few Bings but this is my first dell otro set up.

    Busy week, but I will start with tightening that tube and then go with new plug wires and plugs.

    I will get back.

    Thanks again, and anybody who has a thought, please post.

    PD

  5. #5
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    Since I'm going to start mine for the first time since November today, the thought that comes to mind is stale gas. As an aside, the KTM is the first FI bike I've owned that didn't start in the spring die to stale gas. I'm thinking it's a cylinder size issue.
    61 Gold Star, 76 R90S, 03 CBR600RR, '13 690 Duke, '14 Street Triple R

  6. #6
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    Started '74 R90S last week, under fifty degrees, battery at 12.6 volts, full choke, throttle held slightly cracked, dual plugged, Accel amp, Andrews coils, stock points, rotated very slowly, barely, fired quickly, had to nurse it with the throttle, as soon as it chugged to life, held it at two K, backed the choke off, sat in driveway until it warmed, almost five minutes, slipped the clutch off to under 3K ride around the neighborhood until fully warm.

    This week winter is back and fooling around with valve train. It's really hard on a motor starting it when really cold. The oil (20/50) is so thick it will hardly flow. IOWords, just to run the motor for fun when it's cold, not so good. I never start it once it's put away for the winter. Only when I can ride it will I start it again. FWIW, two sense.

  7. #7
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    So, what I think I am hearing is not to assume my carbs are the problem? Except for the slightly loose intake tube, think more toward ignition?

    Btw, I too don't start my bikes unless I am gonna take them for a ride. I learned that with my dual plugged GSPD.

    Thanks

    PD

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