Misfire or Fuel Issue?

[RVAVMAX]

I have an 89 Max, all stock as far as I know I run 93 octane only in it (Not sure if that's important info or if it even needs to run 93 octane).

Here's the problem, when it is cold or warm but not quite up to full operating temperature she runs beautifully. Now once she warms up fully she sputters and runs terrible. Feel like a fuel issue to me but could it be the coil getting too hot and crapping out too? Hopefully someone else has had this issue!. Thank you in advance.

Graham

 

[maleko89]

Graham, 93 isn't needed. Put in 87 non-ethanol.

I would test all your ignition system components as heat bring a lot of electrical problems to light. Test your plugs, plug wires, coils (primary and secondary windings) and pickup coils. When testing p/u coils use black as the common and not orange as the manual states.

Do you have a test light? When it starts cutting out use the test light on the plug wires and see if it fires regularly.

 

[swedforce]

I would test to turn IN the air mixture screw one half turn... Looks to me that it is perfectly rich for a cold start and up to nearly idle temp, but since the vmax gets richer the more worm it gets so... maby that is the problem....just sitting here on a cold mountain hill and speculate:confused2:what would i know!
and use at least 95 octaneunk:

 

[RVAVMAX]

Thank you for the info. It does have new plugs (1 week old) that doesn't mean they aren't the problem though, so I will start with electrical first and see what that turns up, I don't have a timing light but I'm sure a buddy mine has one. I'm also not an electrical guru or even very well versed in it, so this will be an education experience! I hope I get it figured out though, I can't wait to get her on the road for a nice long ride. What kind of mileage do we average on these things (at a "spirited" pace). Thanks for the pointers I'll get started as soon as I can.

 

[RVAVMAX]

I would test to turn IN the air mixture screw one half turn... Looks to me that it is perfectly rich for a cold start and up to nearly idle temp, but since the vmax gets richer the more worm it gets so... maby that is the problem....just sitting here on a cold mountain hill and speculate:confused2:what would i know!
and use at least 95 octaneunk:

Which screw is the air mixture screw? Also should it be done when the engine is cold, warm, or hot? Thanks again.

Graham

 

[maleko89]

Misfire could occur when lean too. Lean mixture vaporizes easier. One clue is if the temperature gage reads high.

 

[RVAVMAX]

Misfire could occur when lean too. Lean mixture vaporizes easier. One clue is if the temperature gage reads high.

Temp looks good, reads right in the middle, maybe a bit lower... Honestly I'm not looking down there too often, but it looks good to me.

 

[swedforce]

Misfire could occur when lean too. Lean mixture vaporizes easier. One clue is if the temperature gage reads high.

Yes you are right..sorry i would try to turn it OUT...not in (need more fuel). Lucky us there are good mechanics here.:eusa_dance:

 

[maleko89]

Bah! I've made my fair share of mistakes. This forum's nice because it's very active and thus we all get second opinions and corrections! Besides, you are correct....misfire can happen anywhere. Rich conditions worsen as the engine heats up.

 

[RVAVMAX]

Alright move it out half a turn when hot I take it... Now, can anyone tell me which screw to turn? lol. I appreciate the help, hopefully I can get it straight or at least make it a bit better by tonight and ride her around without studdering, popping, and crappy performance.:eusa_dance:

Graham

 

[maleko89]

Yep, go to this post. It has a picture with numbered arrows. Look at arrow labeled #2.

http://www.vmaxforum.net/showthread.php?t=2158

 

[RVAVMAX]

Thank you VERY much, I will give it a shot and hopefully come back with good news!

Edit: I see this on all 4, do I need to adjust them all? Does this thing have 4 separate carbs? I'm a newb to the VMAX, sorry!

 

[copilot777]

Yes all 4 carbs need to be adjusted the same amount .:eusa_dance:

 

[RVAVMAX]

Yes all 4 carbs need to be adjusted the same amount .:eusa_dance:

This oughta be fun! lol, I rode it to work and it was NOT happy about it! Oh well, she will live. I'll give the adjustments a shot when I get home this afternoon. Thank you!

 

[richwrench]

Had a similar mis-fire issue that popped up suddenly last week. Terrible mis-fire & back-fire out of front & rear when hot - I also noticed my tach. was diving down when mis-firing. Because I've had several corroded wiring issues already ( P/O left the bike outside for years ), I took apart every single wiring connector I could find, shot with contact cleaner & packed with di-electric grease before re-assembling. Took for a long ride around the block & it appears that the problem is solved. But since I have all the covers off anyway, I pulled the carbs, reset the floats ( two of them were set at 13mm ) & took about 1/2" of slack out of the v-boost cable. Hope I have time to finish it tonight - should feel like a new bike. My ignition switch connector was the worst - very blue-green with corrosion.

 

[maleko89]

Rich, curous how it runs now! Main switch was bad for me too so I removed the connector and soldered the wires.

 

[RVAVMAX]

I'll have to check all of that out as well, looks like I may have my work cut out for me... Fun stuff!. I don't really care though, I think I got a decent deal on the bike and I love this thing.

 

[richwrench]

Well , got it back together, synched the carbs, set the pilot screws in to 2 1/2 turns, idle at 1100 & went for a road test - OMG it's a NEW BIKE !!! The low speed roll-on power is incredible. As verified the last road test, the mis-fire issue is gone, even after a 5 minute hot-soak at the local 7/11. I pulled out onto Tampa Road, rolled the throttle, backed off for a split sec. & than gunned it & the ass-end started kicking out to the left side as I rocketed forward - my first roll-on burn out ever. NOW I KNOW WHAT YOU GUYS ARE TALKING ABOUT !!! unk: I KNEW there had to be something wrong with my bike - would never smoke the rear tire before - I read all the posts here about burn-outs & I'm thinking " What's wrong - I can't do that on MY Max " well NOW I CAN !!! Don't know what the biggest fix was - the corroded connectors or the floats being so far off - probably a combination of both. I've always had a hot-soak mis-fire even after fixing the hot-soak cranking issue. Whatever dudes, I'm on a whole new machine now - GOTTA LOVE THIS FORUM !!! :clapping:

 

[copilot777]

Well , got it back together, synched the carbs, set the pilot screws in to 2 1/2 turns, idle at 1100 & went for a road test - OMG it's a NEW BIKE !!! The low speed roll-on power is incredible. As verified the last road test, the mis-fire issue is gone, even after a 5 minute hot-soak at the local 7/11. I pulled out onto Tampa Road, rolled the throttle, backed off for a split sec. & than gunned it & the ass-end started kicking out to the left side as I rocketed forward - my first roll-on burn out ever. NOW I KNOW WHAT YOU GUYS ARE TALKING ABOUT !!! unk: I KNEW there had to be something wrong with my bike - would never smoke the rear tire before - I read all the posts here about burn-outs & I'm thinking " What's wrong - I can't do that on MY Max " well NOW I CAN !!! Don't know what the biggest fix was - the corroded connectors or the floats being so far off - probably a combination of both. I've always had a hot-soak mis-fire even after fixing the hot-soak cranking issue. Whatever dudes, I'm on a whole new machine now - GOTTA LOVE THIS FORUM !!! :clapping:

awesome congrats on getting it fixed . have fun and the days of the back tire lasting as long as it used to are gone , lmao unk:

 

[RVAVMAX]

I adjusted the mixture screws 1/4 turn and took her for a spin... no luck. I adjusted them half a turn (total)... No luck... There must be something going on internally if it is a carb issue... I set them where they were origonally. Thank you for the input and advice. I see someone got theirs running well though, AWESOME! Now come over here and fix mine! lol