'48 starting problem

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doc308
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'48 starting problem

#1

Post by doc308 » Mon Sep 07, 2009 2:17 pm

I'm having a real hard time gietting my '48 started for the first time after a rebuild. I'm getting a whole lot of backfiring/sluffing through the carb--what condition would this indicate ? I have a 38mm Mikuni on the bike.



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Re: '48 starting problem

#2

Post by john HD » Mon Sep 07, 2009 2:21 pm

doc,

lean would be my guess.

try more "choke" kicks before turning on the ignition. with a mikuni and an enrichener i would just leave it full on.

my drill is:

gas on
2 full compression kicks with choke full on
raise choke one click
retard ignition about 1/4 to 1/2 of the way
ignition on
crack throttle
kick
when it fires ignition to full advance
open choke
enjoy!


john

razzle51
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Re: '48 starting problem

#3

Post by razzle51 » Mon Sep 07, 2009 2:22 pm

my 1st. thought would be timming

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Re: '48 starting problem

#4

Post by NightShift » Mon Sep 07, 2009 7:31 pm

C'mon Guys! Its sucking air somewheres.

'Spectful,

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Re: '48 starting problem

#5

Post by doug_heisel » Wed Sep 09, 2009 8:57 pm

I just had the same exact Problem after a Fresh rebuild the timing was 180 deg. out of time.

doc308
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Re: '48 starting problem

#6

Post by doc308 » Wed Sep 09, 2009 10:12 pm

All of my timing marks line up--the ones on the gear surfaces, the flywheel mark ( at the rear of the inspection hole), and the distributer marks. The piston is on the compression stroke, when the intake valve is just passed closed, and the points are open at this point. Not to sound dumb, but am I missing something here? Where would the marks be if the timing was out 180 degees?

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Re: '48 starting problem

#7

Post by 49er » Thu Sep 10, 2009 12:42 am

pull cover on front intake pushrod. rotate till it goes up then starts down. start looking for timing mark. get it in the hole about 1/4 way. fully advance timer,having already set points to correct gap. turn timer till points barely open. tighten down timer.retard timing, start engine! if autoadvance timer you must turn the shaft fully advanced while doing this. timing mark will show in hole the same way on either cylendar. you must watch intake valve to see which one is on the compression stroke.

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Re: '48 starting problem

#8

Post by Cotten » Thu Sep 10, 2009 3:34 am

Doc!

No,
You don't sound dumb to me.
"The piston is on the compression stroke, when the intake valve is just passed closed," sounds right,
but the points should just be breaking open if timed, not fully open. You cannot see it without using a test light or something to tell you exactly when they break open.

That's the reason a "static line" or continuity tester is needed, as described in the Service Manual.

But you may still be fighting a dangerous vacuum leak nonetheless.
Never does only one thing go wrong at a time.

...Cotten
PS: On second thought, calling the circuit breaker (or timer) a distributor is kinda dumb.
Indians and autos came with distributors: rotor, cap, and all that.

doc308
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Re: '48 starting problem

#9

Post by doc308 » Sat Sep 12, 2009 1:25 am

Thanks so much for all of the advice, comrads. I have a feeling that my points are opened up too much when all of the timing marks line up--I think that this would suggest overly advanced timing(?). I did get some occasional kickback when trying to start the bike--I think that this might also suggest advanced timing? I'll try a test light to be more precise as suggested. AND.. I 'll stop calling the circuit breaker the distributer !

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Re: '48 starting problem

#10

Post by Frankenstein » Sat Sep 12, 2009 1:36 am

Cotten's right about using the test light to determine exactly when the points are open. However, a shade tree solution that will get you by is using a cigarette paper between the points. When it just pulls free, then the timing marks should line up. Also gives you a good excuse to have that pack of ZigZag's in the tool box when your curious children ask :lol:
It also is a good technique on magnetos where it is sometimes hard to find a place to attach test light leads.
DD

doc308
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Re: '48 starting problem

#11

Post by doc308 » Sat Sep 12, 2009 3:05 am

OK--I used a test light and found that the points were about wide open when the timing mark on the flywheel was seen at the rear of the inspection hole. So, I loosened the nut on the distributer--I mean, circuit breaker/timer , and retarded it ( turning it clockwise), while watching the light. Well, I turned it as far as the adjustment would allow for and the the points were still open a bit more than they should be . In order for the light to go out, I had to manually retard the timer a few more degrees . So, my conclusion is that the timing was very advanced ( and still might be a bit more advanced than it should be even after using up all of the adjustment). If this adjustment is not enough for the bike to start/run smoothly, I assume that I'll next need to pull the timer out of the engine and align the rotor by hand for a perfect timing adjustment--correct? Or is there something else I can do before resorting to that?
(I should note that I can't start the bike right now to really test it out because the generator is out--it'll be back in w/i a week though.)

Thanks again for the guidance--I really appreciate it.

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