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General Category >> Rubber Side Down! >> Missing and backfiring
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Message started by wvhunter62 on 09/24/08 at 11:57:02

Title: Missing and backfiring
Post by wvhunter62 on 09/24/08 at 11:57:02

I have an 87 Savage that until 2 days ago ran like a top. It starts fine, idle is good. When I take off it does fine until about 10mph and then it misses, coughs, backfires until I back off the throttle a little. This continues every 10mph until I reach a top speed of 40mph. I have changed the gas, plug, fuel filter, and cleaned the fuel bowl as well as the jets and needle valve. When I first started it up it ran fine for about 20 minutes and then started again. Could it be electical, like the ignitor or the coil? Also adjusted valves and compression is good. HELP! :(

Title: Re: Missing and backfiring
Post by justin_o_guy2 on 09/24/08 at 12:57:03

Man, unhook the speedo! Its just lazy. If it doesnt know how fast it being forced to run, maybe it wont want to lay down.

Title: Re: Missing and backfiring
Post by EssForty on 09/24/08 at 15:48:22

What do you mean by it happens every 10 mph? Is is happening when you change gears and roll off the throttle at 20, 30 and 40 mph? Or is the sputtering happening exclusive of gear changes?

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/24/08 at 17:01:28

As the RPMs rise it starts to miss at the same rpm in each gear. When you change to the next gear rpms drop it does fine until it reaches the same rpm and it starts to miss again. Also you cannot really open it up, you have to roll the throttle on.

Title: Re: Missing and backfiring
Post by justin_o_guy2 on 09/24/08 at 17:34:45

Carb slide not sliding?

How's the air filter?

Title: Re: Missing and backfiring
Post by verslagen1 on 09/24/08 at 17:37:04

Yep, clean the slide easy to do.

and change the plug.

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/26/08 at 07:58:40

Thanks for the info! I cleaned the slide and she is running better than ever! ;D

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/26/08 at 08:54:17

:'( Ok it ran good for about 2 miles and started again. Slide is moving,has new plug, new fuel filter, new cone filter, starts up and idles perfect. Take off slowly to 10mph, pop...pop pop stutter cough, roll off shift to second, smooth up to 20mph same thing and so on and so on. Seems to clear up for a moment after back firing. Help again :-[

Title: Re: Missing and backfiring
Post by dasch on 09/26/08 at 09:08:54

What about when it's not moving?? What happens then @ 2000 rpm (approx - per your description). Try and post. We go from there.

Also (too lazy to check your profile :-[ ) - is all stock?? Jets, filter, idle mixture screw... Have you changed anything lately?

Title: Re: Missing and backfiring
Post by verslagen1 on 09/26/08 at 09:15:41

ok, so it ran good for 2 miles, ripped thru the gears? everything good?

Then what happened? pushed in choke?

Anybody near you that you can swap parts with? carb... coil... etc.

'87 with how many miles? Have you looked at the cam chain?

How about clogged gas cap? Does it do the same with cap off?

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/26/08 at 09:44:53

Misses while setting still also, Bike is mostly stock, cone air filter, Jardine muffler,carb mix richened about a 1/2 turn. All of this had been done before it started acting up. Slide is moving when bike misses. Cap on or off does the same thing. No black smoke so I don't think its loading up. And every once in a while after it backfires it clears up for a minute or two. Bike has 12,555 miles, choke was in(it misses when choke is on also) coil and ignitor are original equipment(looks like) Have not checked cam chain yet.

Title: Re: Missing and backfiring
Post by verslagen1 on 09/26/08 at 10:03:07

If I remember correctly, this bike is relatively new2u.

I recommend to all new2u bike owners with over 10k to do the cam chain check. It's the best way to know the condition of the bike. And when to take care of this important maitenance item. Although I don't think this is your issue, it's a big question mark that you don't yet have an answer for. Might as well do it so we know this bomb isn't ticking. :o

me thinks it's your coil, check the leads, check the grounds, check the cdi. ;D

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/26/08 at 10:09:06

I was just reading your tech post on the cam chain. I will have to wait till Sunday. Got to take a load of freight to Dayton OH tonight. I'll get back to you Sunday after I check it all out. Thanks again for your help.

Title: Re: Missing and backfiring
Post by justin_o_guy2 on 09/26/08 at 10:15:04

If its missing AND backfiring, cant you just walk toward the sound of the backfire & FIND it? Sheesh,,,

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/26/08 at 10:58:21

You're one of those fellas that holds the plug wire while your buddy cranks the motor over to see if it's getting a spark, ain't ya? :o

Title: Re: Missing and backfiring
Post by justin_o_guy2 on 09/26/08 at 11:48:39

NOOOOO, I'm the guy who hits the starter!

Title: Re: Missing and backfiring
Post by mwilso94 on 09/26/08 at 16:38:09

Hey - I had a problem similar to this not too long ago on my 87 Savage. Turned out my negative battery cable wasn't tight on the battery. Just a quick, easy thing to check.

Title: Re: Missing and backfiring
Post by dasch on 09/27/08 at 04:42:39

So it misses beat under no load as well... Check all connections and jacks in CDI circuit, starting with battery. Loooong and boring job, but...

Also, I would unscrew the tank loose, raise it somehow by inch or two and cranck up the bike at night. Check for sparks leak and funny auras around coil/cable etc... Old trick from 2 decades ago...

Title: Re: Missing and backfiring
Post by wvhunter62 on 09/28/08 at 05:42:35

After I snuck up on it(following the backfire was brilliant) I switched out the coil, checked all connections, and tightened the neg battery cable(it was a little loose)fired it up and put 40 miles on with no problems. Now I guess I can tear into the cam chain thing-a-ma-doodle. I will probably send it to verslagen1 for the mod, it looks much better than the stock version. Thanks for the help everyone.