85 FJ1100 backfires some but then runs well .. Any ideas ?

[big_b]

I just bought an 85 FJ1100 and it has a K&N air filter with a Vance and Hines full exhaust.

It runs really well except at low RPM while applying throttlw steadily between 2,600 to 3,400 RPM it hesitates some and will pop and crack out of the exhaust (backfire ?)

All that I hav read seems to indicate a lean fuel mixture .. So I turned the carb mixture screws on top out to 5 1/2 turns (I know way to much) At that much fuel it backfires less and I really only hear it when I am at 5,500 RPM and 55MPH .. as soon as I give it more throttle it goes away.

The Yamaha mechanic at the dealer said it doesn't sound or feel like (he drove it) the carbs are plugged or needs rebuilt, he said it was to smooth and I propbably had an air leak.

I checked the intake "boots" by spraying some carb cleaner all around and it did want to run rough when I sprayed the 2 inner "boots"   It does not seem like a big air leak .. but is that enough to cause the pops in the exhaust ?

I replaced the exhaust gaskets .. If they are not tight enough would that make the backfire/pop out of the exhaust ?

I ordered new boots and O rings to be safe..
I also have noticed that if the bike is running and I am spraying of the motor to clean it .. it will run rough when I spray water near the #1 plug and wire .. (I ordered new wires too)


The normal mixture setting is about 2.5 to 3 turns out right ? Is that the same with the new exhaust and the air filter ?  Any other ideas ? By the way it runs really storng and smooth above 2500 RPM and I have no smoke from the exhaust ... 

THANKS !

[SkyFive]

I would check the valve clearance while you have the tank off. I bought a 1984 FJ1100 a few months back, with an occasional backfire and when I disassembled the engine for overhaul I found the valves had not touched the seats in a long while. I don't know how it ran at all aside from the carbon that the valves were seating on.

[SlowOldGuy]

I checked the intake "boots" by spraying some carb cleaner all around and it did want to run rough when I sprayed the 2 inner "boots"   It does not seem like a big air leak .. but is that enough to cause the pops in the exhaust ?

I think you've found a problem here.  Take care of one thing at a time.

DavidR.

[big_b]

Thanks .. sometimes I just need to listen to myself !!  The new boots will arrive today and I will try them out tonight. I will post back by tomorrow and let you guys know the results ..

Thanks!

[SlowOldGuy]

Was this the intake boot between the carb and the engine, or between the airbox and carb?

If it's the one between the carb and engine, then definitely replace.  Also replace the large o-rings that seal against the head (40mm ID by 2mm cross section).

If it's leaking between the carb and airbox, then it may just be  a clamp that slipped off.

DavidR.

[big_b]

I replaced the carb boots and O-rings between the carb and intake .. It seems as though it is not backfiring or popping upon applying throttle at all now ...

I have a slight rumble /pop or two on decel .. but nothing that bad .. (Maybe a small exhaust leak)

It is alot harder to start when cold now for some reason .. I have to choke it and warm up for a minute or two .. Is this normal with these bikes ?  I have the mixture screws set to about 3 turns out .. 

THanks

[racerman_27410]

yes you should have to choke the bike to start it first thing.


KOokaloo!

Frank

[big_b]

Great .. looks like I may finally be able to enjoy the bike some .. I am installing a radar detector on it today  

Also, can't wait to try out my new hand grips an new rear tire this weekend !

[RichBaker]

I replaced the carb boots and O-rings between the carb and intake .. It seems as though it is not backfiring or popping upon applying throttle at all now ...

I have a slight rumble /pop or two on decel .. but nothing that bad .. (Maybe a small exhaust leak)

It is alot harder to start when cold now for some reason .. I have to choke it and warm up for a minute or two .. Is this normal with these bikes ?  I have the mixture screws set to about 3 turns out .. 

THanks

If you have an aftermarket exhaust, that light popping is normal and indicates properly tuned carbs. As far as choke goes, I have #40 PJs and if the temp is over 99F or so, I don't need any choke. She does grumble a bit and require a slightly opened throttle 'til she heats up...

[Flying Scotsman]

My 85 FJ1100 has been running great but mpg is bad and it splutters a little if you roll on the throttle.I just tried spraying starting fluid on the intake boots.It caused the bike to die.I thought rpm would increase but just the opposite hapened.I removed the boots and took out the gaskets.They look like flatened o rings.Should they be flat or round like an o,ring ?.I am going to see if I can find some o,rings that fit and test it with starter fluid again.Bike runs awesome other than just on the throttle when it warms up.Sounds like the clasic air leak to me,I will let you know if new o,rings fix it.

[racerrad8]

...I am going to see if I can find some o,rings that fit...

No need to look further than here; O-ring

Randy - RPM

[Flying Scotsman]

 
I just tried to order twice and was denied.

The error report returned by the server was:
(27) The transaction has been declined because of an AVS mismatch. The address provided does not match billing address of cardholder.

I was ordering 4 header gaskets 4 intake boot o,rings 1 needle jet kit and 2 Dual pod air filters.
I dont speak computer or have the patience to figure it out.I found this # and will try it tomorrow Telephone:(209) 844-9831
If that doesnt work I will find some a bit closer so it wont take as long to ship.I could have o,rings by Friday  from the local dealer.

Scott.

[Dan Filetti]

I just tried to order twice and was denied.

The error report returned by the server was:
(27) The transaction has been declined because of an AVS mismatch. The address provided does not match billing address of cardholder.

Scott, if I were you, I'd call your bank, and soon.  AVS = Address Verification System.  This *may* be fraud.  One trick fraudsters do fairly often is to change your card billing address so you will not receive notifications via mail.  If there does not seem to be any fraud, check with them as to the EXACT address they have as your billing address.  They may have it wrong or you may have typed it incorrectly.

FYI.

Dan

[Flying Scotsman]

Just went to my bank online and my order did go though 3 times.Fuck  now I have to contact them and tell them I dont need  2 of the orders.Saw no other activity going on at the bank.

$ 108.86 x 3 when it should be $108.86  .

[Marsh White]

Don't freak out....Randy will fix you up.   The extra charges are probably only pending and will drop off.   Either way...he will take care of you!