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Discussion Starter · #1 · (Edited)
I'm having a really hard time starting the bike.
The first time I try to start everyday it won't start right away, either pulling or not the choke, tried both ways.
It does backfires when trying to start, mainly in the front carb, trying to start a few times drains the battery to the point that the spark is lost although the engine is turning.
I charge the battery again and after a few tries it catches and starts, have checked the battery before starting the process and is fully charged and good.
When starts I don't pull the choke, after warms up a little if I:
Pull the choke on the front carb, cuts off
Pull the choke on rear carb, RPMs rise and engine runs smooth.

After I take it for a ride and is warm will start right away if I'll do it within an hour or so, after 3 hours or so, I have to start the whole process again.

I think is dumping to much fuel on front carb.... WHY?

Both carbs has the same main jets (130) and same pilot jets (45)
Have pods filters and open exhaust.
This as been happening lately, has been starting and running good with this set up for over 6 months.

Opened carbs and they look very clean inside, ran a full tank with seafoam.

83 Shadow 750
 

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Have you checked the valve clearances? If the valves aren't fully seating, that could cause cold-hard starts.......

Phil
 

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I'm having a really hard time starting the bike.
The first time I try to start everyday it won't start right away, either pulling or not the choke, tried both ways.
It does backfires when trying to start, mainly in the front carb, trying to start a few times drains the battery to the point that the spark is lost although the engine is turning.
I charge the battery again and after a few tries it catches and starts, have checked the battery before starting the process and is fully charged and good.
When starts I don't pull the choke, after warms up a little if I:
Pull the choke on the front carb, cuts off
Pull the choke on rear carb, RPMs rise and engine runs smooth.

After I take it for a ride and is warm will start right away if I'll do it within an hour or so, after 3 hours or so, I have to start the whole process again.

I think is dumping to much fuel on front carb.... WHY?

Both carbs has the same main jets (130) and same pilot jets (45)
Have pods filters and open exhaust.
This as been happening lately, has been starting and running good with this set up for over 6 months.

Opened carbs and they look very clean inside, ran a full tank with seafoam.

83 Shadow 750
Partially stuck open carb float on front carb caused by gum on the pins which break loose from engine vibration or heat from the engine. You try to replicate by trying to start the engine cold and if it won't start then using a screwdriver handle rap the front carb bowl several times hoping it frees the float. Then try starting, if it does then you've found your problem.
 

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Discussion Starter · #4 ·
Have you checked the valve clearances? If the valves aren't fully seating, that could cause cold-hard starts.......

Phil
What's the reason for the valve clearance to change, everything was good not long ago, the bike, although is an 83 it only has less than 17k miles, engine has not been open and though the bike is use every week, we don't put a lot of miles on it.
 

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Discussion Starter · #5 ·
Carburators where removed and looked inside, very clean, no varnish, float moving freely.

I FORGOT TO MENTION in my original post!!!!

I can closed the A/F mixture screw on the front carb and there's barely a change in RPM's

If I close the rear carb A/F mixture there's is a big RPM's change.

A/F mixture screws are set 2 3/4 out
 

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Carburators where removed and looked inside, very clean, no varnish, float moving freely.

I FORGOT TO MENTION in my original post!!!!

I can closed the A/F mixture screw on the front carb and there's barely a change in RPM's

If I close the rear carb A/F mixture there's is a big RPM's change.

A/F mixture screws are set 2 3/4 out
If there's no difference in the way it runs when you turn the a/f screw, you have a plugged jet.
 

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Discussion Starter · #8 ·
Alright thanks.

Will remove the carbs again tomorrow and check the main passage, I know the main itself is not clogged, I checked that yesterday when I removed the carbs.

Will also check the A/F screw and the "O" ring.
 

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Not the main jet, the A/F jet in question. That's your idle circuit.
 

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Discussion Starter · #10 ·
I was thinking!!

If a jet is plugged will it be more or less fuel on the starting circuit?

Reasoning:

It seams to be running rich on the front carb, A/F mixture in, reduces fuel and out increase fuel, so, if there's no change when I turn in the screw it means fuel is going in, either thru the A/F screw or somewhere else, not plugged.

If main is plugged, when I open the choke on front carb RPM's should rise and smooth out, but is cutting off the engine, the way I see it is running rich already and when I pull the choke out add more fuel, shutting the engine.

Please correct me if I'm wrong.
 

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Less fuel. Your a/f passage is partially plugged. When you turn the screw in from 2/3/4 out your not restricting fuel until almost closed. How have you determined the one cyl is running rich. Have you pulled and inspected the plugs?
 

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Discussion Starter · #12 ·
Removed the plugs when "won't" start and they're soaked in fuel.
When I finally got it running I remove then after a good 10/15 miles run and they're light brown, the way they should be, I know how to read plugs.

Going to look into A/F screw and passage tomorrow, maybe the "o" ring started to brake down and a piece is clogging the passage.

Thanks a lot, will continue tomorrow, going to bed now, long work day ahead.
 

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Discussion Starter · #13 ·
Already, removed the carbs again today, removed the A/F mixture screws and check the passages, no plugged, also blew air thru and is coming on the intake side. so I don't think is a problem there.
In the process of removing the screws the "o" rings where stock at the bottom so when I tried to remove them they got damaged. I'm going to try Ace hardware tomorrow if they don't have it, I have to order online and that will take a while.
What will be the best place to order them from?
 

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Already, removed the carbs again today, removed the A/F mixture screws and check the passages, no plugged, also blew air thru and is coming on the intake side. so I don't think is a problem there.
In the process of removing the screws the "o" rings where stock at the bottom so when I tried to remove them they got damaged. I'm going to try Ace hardware tomorrow if they don't have it, I have to order online and that will take a while.
What will be the best place to order them from?
I'd go to your local Honda dealer to see if they have them in stock. If not ask them for the OD and ID dimensions and check your local automotive parts retailer for a replacement of the same size. Otherwise you can check out this site on the web Metric Parts Outlet | Yamaha, Honda, Kawasaki, Suzuki, Arctic Cat USA, AR Contact Via Email
 

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How old is this battery you're using? That bike needs a good battery with a good charge to generate enough spark to fire well. That may be why it's starting right after you recharge it. If you're using a known to be good battery, then you may want to check your charging system to make sure it's doing it's job properly.
 

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How old is this battery you're using? That bike needs a good battery with a good charge to generate enough spark to fire well. That may be why it's starting right after you recharge it. If you're using a known to be good battery, then you may want to check your charging system to make sure it's doing it's job properly.
Agree. Thought of the same thing when the OP first posted. ;)
 

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Discussion Starter · #18 ·
The battery is a year old.
Battery test good, took it back, still under warranty, they did the test.
I have good spark in both jugs, tested sparks with spark tester.
 

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Discussion Starter · #19 ·
No luck at ACE, will go to lawnmower equipment repair place.
Dealers down here in Miami are not to helpful, called the dealer, they said right away they don't have the information but he can get me the A/F screws for about 25 each and takes about 10 days, go figure.

Checked Metric Parts Outlet, they have the screws at about 10 each, don't show the o rings by itself, if I don't find anything locally I will have to bite the bullet and spend 30 for 2 o rings, wonderful !!!
 

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If you get in a pinch, check McMaster-Carr online. They're an industrial supply house outside of Chicago I occasionally use. You can probably get a pack of 25 of those O-rings for a few bucks. When I can't find what I'm looking for locally, I go there as they have everything and anything.
 
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