Backfiring out of left side only

[virago111]

Hello everybody. I just got (June 19th, Fathers day no less) my second hand-me-down bike from my dad

The first was a 1982 Virago 750 and now...... A 1985 V-max!
Only real downside is that it has 56,000 miles, eek!
Well last spring he was thinking of giving it to me and when he fired it up he had a mini disaster, a carb fire....

Well, a year later he completely rebuilt the carbs and got it to me.
So the fun starts. Bad battery, hard starting, replaced battery, did crimp fix, bike runs.....
Take it for a ride and it runs ok but some backfiring out of left side only.
Trimmed 3 of the four plug wires, where they go into the coils (all had some green corrosion)(how do you get at the coil for the front right cylinder, the one pointing right?) and it runs smoother, but still backfiring.
The bike also seems to have some intermittent hesitation below ~3500-5000RPM.

I was thinking any and all of the following could be the issue:
Bad gas (been sitting at dads)
Plugs (gap or fouled)
Wires (Original)
Exhaust leak
Valves out of adjustment
Carbs out of sync
Carbs have a partial jet blockage.

So I was wondering if I should attack this list in any particular order, or is there something else that I should try first.

Any help would be much appreciated.

 

[Rand-5107]

I like your sissy bar and rack. I could really tie a big load of crap to them. I like your list. I think I would move leak and valve adj. to the bottom and add compression test when you change plugs. Drain old gas from tank and carbs. But that's just me. There are far better mechanics here than me.

 

[virago111]

Thanks, I've been reading a LOT of posts to get that list and just want to have the best chance of success when I go after the problem.
Did you notice the UGLY rear fender the guy prior to my dad put on it?!
He got into an accident and broke the original.
My dad said he thought this one made it look mean, I think it makes it look like a$$!
Been looking at the underside to see if all the mount points are still good to try and reconstruct the original with new/used parts.

 

[tugla]

before you get into a full carb clean again, try the peashooter and better the shot gun to help clean them out, also some seafaom in the tank with the fresh fuel, about 4oz.

check the sync, and a/f screws are all roughly the same, any mods like stg 7? i see you got kerker slip ons. how you like the sound of those, ive never heard them.

do you know what jets are in the carb?

 

[maxcruiser]

With Kerker slip ons and backfiring from left side only means that either front left cylinder and right rear cylinder is the issue (I think that's right ones - but to be sure, check which headers run into that Kerker pipe) as there is no crossover at the back since muffler is gone) I would guess rear right cylinder has a carb issue.

Now backfiring while decel or accel or both? Also what do the sparkplugs look like?

Maybe as simple as a air/fuel circuit is plugged up (than do shotgun/peeshooter cleaning method) or loose/cracked intake rubber or improper carb settings.

Also, 56,000 miles is nothing if it was maintained and not over abused. A compression and leak down test will tell you how good the engine is.

Mike

 

[m-cman]

My Kerker slip-ons do have a cross-over pipe.

 

[SpecOps13]

Man, you have a Very Cool DAD.... Guess I'd do the same for my son if he lived 6,000 miles closer...
Welcome to the Best Forum going.. You are taking a very good course of action. Fix it all a step at a
time... BTW, Nice Bike.. And 50k Miles is nothing to a VMax...

 

[virago111]

before you get into a full carb clean again, try the peashooter and better the shot gun to help clean them out, also some seafaom in the tank with the fresh fuel, about 4oz.

check the sync, and a/f screws are all roughly the same, any mods like stg 7? i see you got kerker slip ons. how you like the sound of those, ive never heard them.

do you know what jets are in the carb?

I've been trying to build up the courage to work on anything carb. related, I just want to be able to ride! Thanks for the suggestion, that was exactly what I read here on the forum and it seems to be within my capabilities... Just working on my mojo.....

No mods, that I know of, other than the Kerkers & the butt ugly tail assembly.
The Kerkers are loud but I have no frame of reference as I've never heard the bike without them.... The Kerkers are REALLY LOUD when it backfires out of them....:rofl_200:

Similar comment on the sync, really scared on that one... Besides I don't have the tool to do the job.

My dad told me he never changed anything on the carbs. but who knows what the previous owner did to it.:ummm:

 

[virago111]

With Kerker slip ons and backfiring from left side only means that either front left cylinder and right rear cylinder is the issue (I think that's right ones - but to be sure, check which headers run into that Kerker pipe) as there is no crossover at the back since muffler is gone) I would guess rear right cylinder has a carb issue.

Now backfiring while decel or accel or both? Also what do the sparkplugs look like?

Maybe as simple as a air/fuel circuit is plugged up (than do shotgun/peeshooter cleaning method) or loose/cracked intake rubber or improper carb settings.

Also, 56,000 miles is nothing if it was maintained and not over abused. A compression and leak down test will tell you how good the engine is.

Mike

I'm pretty sure there is a crossover. Besides when it backfires there is only the pulse from one pipe, the left one..... If there was a crossover I'd think I'd feel the pulse in the other pipe, no? The logic path you are taking is what made me check the wire to coil connection. I can't seem to access the front coil that points to the right side without moving the hose/thermostat assembly on the right side. Do I just remove the temp/tach assembly to get at it? That is the only wire I haven't eliminated corrosion from.

The backfiring is mostly on deceleration. There seems to be the hesitation on acceleration that is similar in frequency to the backfire on deceleration.... This is why I think this is a single cylinder issue.

The shotgun/peashooter seems to be in my future....

Really considering the contaminated tank problem as a big red flag here.... Looks like I'll go down that path soon too...

Dad says the intake rubber was changed 2 years ago when he had it serviced..... Also said he didn't have these issues prior to the rebuild he did after the mini fire....

Again my dad said he had no compression issues when he last had the bike serviced right before he put the bike in storage & before the mini fire....

Perhaps I need a pro to diagnose the sync / carb.:damn angry:

 

[virago111]

Man, you have a Very Cool DAD.... Guess I'd do the same for my son if he lived 6,000 miles closer...
Welcome to the Best Forum going.. You are taking a very good course of action. Fix it all a step at a
time... BTW, Nice Bike.. And 50k Miles is nothing to a VMax...

My dads the BEST:thumbs up:

I plan on the step by step process..... I just want to RIDE!!!!
As you can tell from my opening post I've been waiting a whole year since he told me he was giving it to me.... Imagine that I had to suffer with that all last summer.... Oh the humanity!!!!:surprise::biglaugh:

Thanks on the nice comment on the bike.... Lots of oxidation and the clear coat is starting to crack/peel. Looks like a nice winter project to pretty it up! I also hate the rear fender that adds a whole Frankenstein look.:icon_rolleyes:

 

[Thevmaxrider]

My gut tells me this is a carb problem. You might want to try some "Start your Engines" from Golden Eagle products. It is available at AutoZone for sure. Some of the guys here have had good results with it in removing varnish etc. from carbs. At $7.99 a bottle it is pretty cheap and if it works it will save you a ton of grief.

 

[virago111]

My gut tells me this is a carb problem. You might want to try some "Start your Engines" from Golden Eagle products. It is available at AutoZone for sure. Some of the guys here have had good results with it in removing varnish etc. from carbs. At $7.99 a bottle it is pretty cheap and if it works it will save you a ton of grief.

I'm glad that is the case.... I have a new bottle of SeaFoam & "Start your Engines" at home sitting on the toolbox!!!

I wasn't sure which to try first.
I just filled up and drove ~15 miles.
Should I add the recommended ratio to a full tank or get down to ~1 gallon and add the recommended ratio to the lesser amount?

I've got so many ideas bouncing around on what it could be & I'm trying to prioritize so I can get RIDING!!!:rocket bike:
Thanks,

 

[virago111]

My gut tells me this is a carb problem. You might want to try some "Start your Engines" from Golden Eagle products. It is available at AutoZone for sure. Some of the guys here have had good results with it in removing varnish etc. from carbs. At $7.99 a bottle it is pretty cheap and if it works it will save you a ton of grief.

Well I got a chance to look at the exhaust with the bike on the center stand and low and behold there is a bolt missing from the front section joint.:eusa_dance:

So.... Here is the problem. I cant see any threads in the hole!!!

The part number for this bolt is 90101-06576-00 and I'm going to try and see if I can get one to go in there and seal up the leak!

If the hole is stripped any ideas on what would heal up this hole?

 

[Fastatv]

Well I got a chance to look at the exhaust with the bike on the center stand and low and behold there is a bolt missing from the front section joint.:eusa_dance:

So.... Here is the problem. I cant see any threads in the hole!!!

The part number for this bolt is 90101-06576-00 and I'm going to try and see if I can get one to go in there and seal up the leak!

If the hole is stripped any ideas on what would heal up this hole?

Congrats on the Max and yes...you must have a cool/generous
Dad. I've read all the posts and I was going to mention a possible loose exhaust. In regards to not seeing any threads...well I guess it's possible that the stud/bolt could be broken off. I've not had good luck with easy outs...usually end up breaking them and making matters worse. Drill/tap? Keep us posted and good luck!

 

[KJShover]

If the hole is stripped any ideas on what would heal up this hole?

Tap it and then put in another drain bolt.

I have the stock front pipes from my '07 that are hanging in the garage collecting dust. They didn't get much milage on them cause I went with a Kerker system pretty quick. Your more than welcome to them, just cover the cost of shipping.

 

[virago111]

Well I went to my local Yamaha dealer and the tech there found some replacement bolts and copper washers and plugged the holes in the exhaust.

Here is the kicker.... FOR FREE!!!! Almost fell over on that one. Almost feel committed to go back for service...... NOT!!! None the less a nice gesture from C&E Yamaha in Middleboro, MA.

Anyways, the backfiring has been reduced but it still happens on moderate to heavy deceleration. Thinking a carb sync is in the cards.
I did a tank of seafoam and now my idle went from 1000 to 1500 almost overnight.

All in all I'm getting to know this bike, and DAMN it is fast. Need to be careful not to get a ticket.... Or kill myself... Wee!!

 

[gamorg02]

which dealer is that, i'm not that far away?

 

[virago111]

which dealer is that, i'm not that far away?

http://www.ceyamaha.com

 

[virago111]

Tap it and then put in another drain bolt.

I have the stock front pipes from my '07 that are hanging in the garage collecting dust. They didn't get much milage on them cause I went with a Kerker system pretty quick. Your more than welcome to them, just cover the cost of shipping.

I'm interested, but two questions:
1. Are the pipes the same
2. If they are, any idea on the cost to ship to Kingston, MA 02364?

 

[KJShover]

Need to be careful not to get a ticket.... Or kill myself... Wee!!

You can always pay the ticket. A life on the other hand, not as easily replaced.

I'm interested, but two questions:
1. Are the pipes the same
2. If they are, any idea on the cost to ship to Kingston, MA 02364?

I think they are, I belive it was the muffs that got changed and not the pipes after '85. let me pack them up and get a size and weight. Then I can get a shipping cost.