SuzukiSavage.com /cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Trouble Diagnosing Stutter /cgi-bin/YaBB.pl?num=1245782493 Message started by Topher on 06/23/09 at 11:41:33

Title: Trouble Diagnosing Stutter Post by Topher on 06/23/09 at 11:41:33 Hello, thumpers. Been reading this great site for a while, and now I have a problem. A couple pro mechanics have said “maybe-this-maybe-that.” My repair ability is strong, but knowledge is spotty. Anyone want to play the diagnosis game? 2001 Savage, 8,000 miles, 4,000 of those since bought a year ago. Warm weather, above 70 degrees: Bike always starts and runs with no problems. Cool weather: Bike starts fine, but dies or stutters awfully once warmed up. Starting  behavior is same whether use choke to start (colder air temp) or do not (at 60-70 degrees). After a couple minutes of warming, and when choke turned off if used, revolutions slowly decrease until stall. Can restart with much throttle, so much that gas may come out carb vents. On restart revolutions are normal, but slow to stall again. There is a small amount of black smoke from tailpipe when giving gas to keep alive. Riding behavior (if take off before warm, or ride into cool weather): Couple minutes after starting, engine stutters horribly for a few seconds (chugga-chugga, power loss), then runs well for 10 seconds, then continuously repeats this cycle. Dies at idle. Can usually keep running with continuous, generous throttle. Running at high RPM does seem to help when behavior less severe (moderate air temps). Problem appeared suddenly. This was after a couple months garaged in winter, with no storage prep, but had been riding again for several hundred miles. Have very mild leak from head gasket since purchase, one year. (At least I think it’s head gasket.) Fixes Tried: Replaced spark plug (blackly caked). No change. Bike shop didn’t experience behavior. Thought it rich and leaned mix half turn; put ring clean in gas. No change. Higher (medium) octane gas. No change. Tried carb cleaning, with limited knowledge/ability. Both ends of air horn and the bowl looked pristine clean. Float traveled freely and no apparent damage. Throttle plate moved freely. Cleaned nothing; didn’t know how to check anything else. Pro mechanic friend suggests I replace the ignition coil next.

Title: Re: Trouble Diagnosing Stutter Post by Mr. Hyde on 06/23/09 at 11:53:28 First guess would be turning the idle up when it's cool although I don't know what you mean by cool in North Carolina.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/23/09 at 12:00:09 0E316D0B3A2726430 wrote: First guess would be turning the idle up when it's cool although I don't know what you mean by cool in North Carolina. Afraid that's too simple. Won't deal with stutter at speed, and really, it's worse than that. When I say awful and horrible stutter I'm serious. (Cool is at or below 70 degrees.)

Title: Re: Trouble Diagnosing Stutter Post by cowspotter on 06/23/09 at 12:42:14 Maybe stilll running too rich? You said the spark plug was really blackened, which would indicate a rich condition. That doesn't make too much sense though when it only happens when cold. Cold air is denser, so more oxygen, so i would expect that to lean out the combustion, not cause it to be more rich.

Title: Re: Trouble Diagnosing Stutter Post by AngloSaxon on 06/23/09 at 12:54:40 The standard jetting on the Savage is pretty poor. Contact LANCER, he has jet kits for sale. He can also give you a few other ideas about what could be wrong. Could also be dirty air filter. Cheers.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/24/09 at 06:38:09 38342C282B342F2F3E295B0 wrote: Maybe stilll running too rich? You said the spark plug was really blackened, which would indicate a rich condition. That doesn't make too much sense though when it only happens when cold. Cold air is denser, so more oxygen, so i would expect that to lean out the combustion, not cause it to be more rich. My current working theory also focuses on the seeming richness. I'm thinking incomplete combustion. But I can't match that to all the symptoms, either. And the cause of it would still be unknown to me.

Title: Re: Trouble Diagnosing Stutter Post by ero4444 on 06/24/09 at 09:09:20 Try cleaning air filter or for a test, just take it out.  Don't run long without a proper filter though. Does it run any different when petcock is set to PRIME?   Battery in good shape at least 12.3vdc (50%)  or 12.6vdc(100%)? The mild oil leak is probably the very common and minor cap plug over a head bolt - my drips don't reach the ground yet either.

Title: Re: Trouble Diagnosing Stutter Post by Rockin_John on 06/24/09 at 11:01:17 Here is why your "pro mechanic" friend is recommending changing the ignition coil next: Because of the temperature dependency of the symptoms. I've experienced a couple of very frustrating episodes with a couple of different vehicles over intermittent shorts (or opens) of the coil windings. What happens is that the "open" in the winding of the coil is such a small gap (close together); that the warm/cold conditions cause the coil to work intermittently. The added vibration of working right next to a shaking engine doesn't help the situation any either. So any mechanic who has been around a long time has run across this very frustrating multiple changing symptom problem from an ignition coil before. And once it happens to you and makes you rebuild you carbs, check your vacuum; cylinder compression; valve lash, and everything else in the world you can think of... you never forget how it turned out to be the stupid coil all along!  ::) ;) However (and there is ALWAYS an exception) I would still check everything easy and less expensive before shelling out $75 or so for a brand-new (known good) coil. (Actually, I wouldn't have to do that; because besides having 3 Savages to scavenge parts between for testing, I also bought a supposedly good coil in a box of misc. Savage parts off or eBay not too long back.) In fact, if you need a loaner coil for diagnosis, I'll let you borrow one for the cost of shipping it back and forth; but I ultimately want my spare back; because having 3 Savages I figure I'm bound to lose one sooner of later. I've been buying up other known-to-fail parts as they come through eBay too. Got a spare set of shifter rods in the box with the coil... Still in bad need of a late model (95+) front brake master cylinder myself though. They seem to be hard to come by used. Let me know if you get to the point you want to try the coil... John

Title: Re: Trouble Diagnosing Stutter Post by diamond jim on 06/24/09 at 15:04:26 I've been able to reproduce the symptoms you mention three different ways- air, fuel and vacuum.   Air filter.  From my experimenting with various filters and filter media: a little too restrictive- idle fine, rev fine, slow accelerate fine with very casual riding up to about middle rpm range, start to stutter under medium spirited riding, cough and sputter under full throttle and high engine load. moderately restrictive- idle fine, start to stutter when revving, stutter when slow accelerate with very casual riding up to about middle rpm range, cough and die with full throttle or high engine load. very restrictive- stutter when idling, and revving kills engine. Fuel. Tired of putting the tank after doing some work to see if she runs, I made a test gas tank out of a plastic water bottle, lawnmower gas filter and clear fuel line.  The filter is mounted to the bottle cap. Just fill, hook other end of the line to the carb, turn bottle upside down and viola.  The other day I used some gas out of a gas can that had been sitting in the garage for maybe 6 months.  Started, idled a little rough, stuttered with any revving.  Emptied fuel bowl, filled bottle with gas from the tank, primed, started, ran fine.   Vacuum.  When I first used the bottle I didn't plug the vacuum line.  Started, idled a little rough, stuttered with some good revving then got progressively worse. Air, fuel, vacuum.  Always check them.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/26/09 at 09:37:28 Thank you very much guys. VERY helpful info here. I have a new "problem." Carolina has reached the season where it never gets cool enough to cause my problem. I can't diagnose anything now! I will do some of these suggested checks and maintenance, but we may not know whether they help until fall. My bet -- problem returns and you'll hear from me again, then. Thanks especially to Rockin_John for the loaner offer. I might take you up on it when the behavior returns. ero4444: Can't do those tests now, but will remember. diamond jim: Very useful info for my diagnosis. I did forget vacuum! Why do we always do that?  ::)

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/26/09 at 09:49:32 And here's a new observation from the last cool day. Re. head gasket: While using much throttle to prevent stall at idle, I saw a tiny but vigorous pfft-pfft-pfft of something gaseous coming from the front center of the head gasket.  Is this definitely the problem or just highly suspicious? How serious is that behavior?

Title: Re: Trouble Diagnosing Stutter Post by Yonuh Adisi on 06/26/09 at 11:32:47 0D3629313C2B590 wrote: And here's a new observation from the last cool day. Re. head gasket: While using much throttle to prevent stall at idle, I saw a tiny but vigorous pfft-pfft-pfft of something gaseous coming from the front center of the head gasket.  Is this definitely the problem or just highly suspicious? How serious is that behavior? That sounds like the infamous plug cap leak. The other stuff, no offense to anyone here but it seems to me that they are wanting you to go around your a$$ to get to your elbow. Check the petcock and vacuum line.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/26/09 at 20:52:31 I spoke too soon. Problem came back with a vengeance tonight at 80 degrees. Never happened at that temp. Very humid. And... setting petcock to Prime cleared it right up. Switching back and forth several times confirmed. What does this test tell me?!  That the problem is in vacuum or petcock as Yonuh suggests?

Title: Re: Trouble Diagnosing Stutter Post by ero4444 on 06/27/09 at 19:04:27 I think it means "replace 8-year-old petcock" with easy manual Raptor petcock, or your vacuum line leaks.  Replace line first I guess - seems easy but I've not had to do it myself yet. It's still possible that crap, rust, grit in the tank has clogged the (normal) FUEL port - does it run ok in RES?  I wonder if PRIME gravity-feeds the gas from the RES fuel port. Funny that the plug is black suggesting the burn is rich but I don't know enough about engines or carbs.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 06/28/09 at 15:56:22 OK, that's how I read it too. Will think about the RES thing. The plug I changed could have been original as far as I know, so it may mean little. Thanks for help! I didn't even understand I had a vacuum operated petcock a week ago. Talking helped me figure out new things to look up. Fingers crossed now.

Title: Re: Trouble Diagnosing Stutter Post by Rockin_John on 06/28/09 at 16:35:49 0A312E363B2C5E0 wrote: I spoke too soon. Problem came back with a vengeance tonight at 80 degrees. Never happened at that temp. Very humid. And... setting petcock to Prime cleared it right up. Switching back and forth several times confirmed. What does this test tell me?!  That the problem is in vacuum or petcock as Yonuh suggests? Yup, if you get consistent results from changing the petcock position, that eliminates the probability of anything but the vacuum hose or petcock itself as the culprit. Fix/replace those, and hope it is the end of your troubles!  ;) Still sucks that there is no rebuild kit available for our petcock. And I don't understand it since there are so many others of similar design which kits are available for. Just a case of Suzuki trying to nick all the Savage owners for an extra $50-$60 after a few years ownership it appears. Sell up a bike cheap; then make their profit/markup by selling us overpriced parts for years thereafter? Doesn't speak too well for Suzuki's long term commitment to customer loyalty. Bad news is: They aren't the only company who has that type of attitude nowadays.

Title: Re: Trouble Diagnosing Stutter Post by Digger on 07/05/09 at 21:30:07 Topher, Check out this thread: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1152108113/0 When you are done reading that thread, you can try this test: Crimp the petcock vacuum line so that nothing can get through it. Select PRI on your petcock and ride the bike.  If it runs good like that, you most likely have a leak in the petcock diaphragm that allows gas to leak directly into the intake manifold, causing a rich condition. You can ride it like this, but don't forget to select ON or RES on the petcock before walking away from the bike. Report back up w/ your findings, please - good luck! IHTH!

Title: Re: Trouble Diagnosing Stutter Post by Topher on 07/08/09 at 13:54:59 :D Looks like we have a winner! The petcock. There was gas in the vacuum hose. I've removed and capped the vacuum line, and am operating PRI/FUEL as ON/OFF, just like the good ol' days. For a permanent solution I think I will put on a Raptor petcock, while putting a stronger seal on the carb's vacuum port. (Is it true those rubber caps fail?) No more problem, even on one nicely chilly, late night ride. Until... my shift linkage broke! Rode home from the corner store in first. Dang, if it ain't one thing...!  (Easy fix though.) Amazing thread, Digger--exactly the same symptom and result! Shame I didn't find that sooner. I appreciate everyone's help a lot! Even the comments that weren't the final answer helped me learn a lot while researching them. This is why we board, because talking it out works.

Title: Re: Trouble Diagnosing Stutter Post by tomtaz1975 on 07/08/09 at 15:20:16 Not to hijack the thread, but I have been having the EXACT same problem...I think.  No matter how I warm her up, I have to give her gas at idle just to keep her running when at a stop sign or red light, even with idle set high.   I did get a raptor but haven't installed it yet.  I can't find the thread/help that shows how to deactivate the vacuum hose.  Can anyone help me find that thread showing what to do with the hose?

Title: Re: Trouble Diagnosing Stutter Post by Yonuh Adisi on 07/08/09 at 15:40:49 263D3F263328636B6567520 wrote: Not to hijack the thread, but I have been having the EXACT same problem...I think.  No matter how I warm her up, I have to give her gas at idle just to keep her running when at a stop sign or red light, even with idle set high.   I did get a raptor but haven't installed it yet.  I can't find the thread/help that shows how to deactivate the vacuum hose.  Can anyone help me find that thread showing what to do with the hose? After you put the raptor petcock on, you stick a hose on the vacuum port of the carb and stick a screw in it, or get a vacuum cap from an auto parts store and plug the port with it.

Title: Re: Trouble Diagnosing Stutter Post by Topher on 07/08/09 at 17:12:28 4D56544D584308000E0C390 wrote: Not to hijack the thread, but I have been having the EXACT same problem...I think.  No matter how I warm her up, I have to give her gas at idle just to keep her running when at a stop sign or red light, even with idle set high.   I did get a raptor but haven't installed it yet.  I can't find the thread/help that shows how to deactivate the vacuum hose.  Can anyone help me find that thread showing what to do with the hose? OK, passing forward my new found, brilliant insights...  ;) Of course, install your Raptor if you want and see if that's a fix. In the meantime, as above, you might try running with petcock set to PRI. If that solves your problem, you do have the same situation and either the vacuum hose or petcock are bad. Also, check the vacuum hose after operation for gasoline in it. It might not be much, I used a taste test (yechh!). That means leaky diaphragm in petcock, which is apparently unfixable. If that doesn't prove a problem in this area then you're back to square one on diagnosis. Clogs in the petcock still might be an option, but not any more obvious than many other things that someone smarter can talk about. The vacuum problem is ruled out, because PRI is not vacuum operated. The vacuum hose is mostly discussed only in passing. It is the smaller one running from petcock to a port on the carb on the opposite (right) side. Many deactivation methods are proposed. I removed it and used rubber caps from parts store under $2 a half dozen. Some say they will rot. Or cut the hose and clamp it. Or cut the hose and seal with a screw and some gasket sealer. Or I think some have put said screw seal right in the ports. Anyway, the carb's vacuum port must be sealed if not used. If vacuum deactivated (you may know this) you run on PRI, and turn to FUEL (which is now OFF) when engine is off.

Title: Re: Trouble Diagnosing Stutter Post by Digger on 07/12/09 at 21:07:40 455E5C45504B00080604310 wrote: .....I can't find the thread/help that shows how to deactivate the vacuum hose.  Can anyone help me find that thread showing what to do with the hose? Tom, Many ways to block the carb's vacuum port. Here's how I did it.....it's cheap and effective: http://i235.photobucket.com/albums/ee201/Digger109/CarbVacuumPortPlugE.jpg I just cut off a section of the existing vacuum hose, squeezed some silicone sealant in it, folded it over, and held it folded with two small zip-ties.  Then, I plugged it into the carb's vacuum port. IHTH!

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