SuzukiSavage.com - Engine Missfire at High Revs

stuartross109 Ex Member	Engine Missfire at High Revs 05/24/07 at 11:19:59 Hi out there Can you help I have a 1986 Savage that has developed a missfire at full throttle openings. It only occurs at full throttle and goes if I back off the throttle. The missfire has a regular popp, popp popp! I have cleaned out the carb but this makes no difference. Any help please?
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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10661 Oklahoma Gender:	Re: Engine Missfire at High Revs Reply #1 - 05/24/07 at 12:33:11 Is the alternator getting weak, and for now is only showing up at the high power end where the most stress to the ignition system is made?
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justin_o_guy Ex Member	Re: Engine Missfire at High Revs Reply #2 - 05/24/07 at 17:24:29 Can this be spark plug related? Sure would be easy to look into & cheap t fix.They can start to break down at higher rpm, right?
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bduff YaBB Newbies Offline Posts: 30	Re: Engine Missfire at High Revs Reply #3 - 05/24/07 at 18:35:21 I would start with a new spark plug
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clueless-FSO Senior Member Offline Posts: 454 Birmingham, Al Gender:	Re: Engine Missfire at High Revs Reply #4 - 05/24/07 at 19:38:46 I would check all the electrical connections, starting at the battery.
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tx650 YaBB Newbies 2005 No Login Offline I love YaBB 1G - SP1! Posts: 7	Re: Engine Missfire at High Revs Reply #5 - 05/24/07 at 22:02:08 Had same problem with my 88. Ran a jumper wire from positive side of battery to o/w side of ignition coil and it ran fine. Found too much voltage drop to coil because of bad side stand relay.
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stuartross109

Ex Member

Re: Engine Missfire at High Revs
Reply #6 - 05/25/07 at 12:24:59

Thanks for all your suggestions. I don't think its plug related as I have just fitted a new one and it has a good spark but it is worth a try. I will try the suggestion with the wire.

Having had a look at previous messages I looked at my cam chain tensioner and it was about to go (27000 mls). It gave no real tension to the chain so I wonder if this is part of the problem.

I will try the suggested mod. Will keep you posted.

This is probably covered elsewhere but can I replace the chain without taking the head off?

Thanks

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verslagen1

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Re: Engine Missfire at High Revs
Reply #7 - 05/25/07 at 12:37:38

No, replacing the chain can't be replaced thru the head.

All you need to do is remove the clutch cover and check the tensioner projection. More than 18mm from the housing to the shoulder and it's time to be worked on.

If it does, you'll need to remove the head cover. Optional at your discretion is the welded tab slavy mod. Check out the cam chain library in the tech section. But I would recommend measuring the chain stretch before you decide which way you go.

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justin_o_guy Ex Member	Re: Engine Missfire at High Revs Reply #8 - 05/25/07 at 14:49:15 Did you put that new plug in after this started? Just before? If it started just after the new plug, be aware, new doesnt mean good.
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stuartross109

Ex Member

Re: Engine Missfire at High Revs
Reply #9 - 06/28/07 at 13:17:43

Have tried new plug and re-cleaned the carb. Model does not have side stand relay.
On reflection the missfire is not so much at high revs as wide throttle openings. The bike will rev well as long as it takes its time on up ro 3/4 throttle opening. Open it wide and it starts to missfire straingh away. Back off and it stops. Seems carb related but the thing is clean and sound. I would have thought wrong size main jet but ran fine previously.
Any other thoughts?
Stu

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Savage_Rob Serious Thumper Alliance Member Offline Mechanically Inclined Amateur Posts: 6972 Texas (Dallas area) Gender:	Re: Engine Missfire at High Revs Reply #10 - 06/28/07 at 13:47:24 Check for exhaust leaks. If one of your exhaust gaskets is leaking, it can allow air to be sucked into the exhaust stream and cause postignition of unburnt fuel.
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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10661 Oklahoma Gender:	Re: Engine Missfire at High Revs Reply #11 - 06/29/07 at 08:23:33 Are you checking the plug for an overly rich condition?
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stuartross109 Ex Member	Re: Engine Missfire at High Revs Reply #12 - 06/30/07 at 10:04:22 Hi Does look quite rich. Any thoughts as to possible causes? Stu
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barry68v10 Serious Thumper Offline Posts: 955 Maryland Gender:	Re: Engine Missfire at High Revs Reply #13 - 06/30/07 at 11:13:05 As soon as I read this thread, my first thought was too big main jet...do you know what's in it?
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Serowbot

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Re: Engine Missfire at High Revs
Reply #14 - 06/30/07 at 11:48:23

Check for fuel in the carb's vac line. Probably not the problem but, it's so easy to rule out. Any gas at all in there and that's your problem.
Also make sure the line is fitting the nipples securely.
Next I'd look for a sticky slide. You check that by removing the four screws from the top of the carb. Carefull they tend to strip out. Replace them with allen heads, if you go there.

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Ludicrous Speed !... ... Huh

...

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