XS750 Backfiring But Not Starting

[750triples]

Hello everyone,

Just like the title says, when I crank the bike it’ll make some loud pops but it won’t start. After cranking it for a long time it will start and idle fine, but obviously that’s not ideal. When I’m cranking it it stinks of unburnt gasoline.

Spark is all good, fuel is new.

 

[jetmechmarty]

If if runs fine after it starts I would suspect a fuel issue. The carb guide in the tech section should help.

 

[750triples]

I turned my mixture screws in (clockwise) 360 degrees, and after a lot of cranking it decided to start up. I’m running pods, so my jets are up two or three sizes, I don’t remember.

Now that I’ve turned the screws in, the bike will only start when it’s ice cold and on choke (before it wouldn’t start at all, just backfire). It can’t idle off choke, it just dies.

 

[Signal]

Probably been asked in other threads, but have you checked the pod filter mounting flange is not covering the idle jets when they are mounted. Some pod filters have a large internal ridge that does.

 

[750triples]

Probably been asked in other threads, but have you checked the pod filter mounting flange is not covering the idle jets when they are mounted. Some pod filters have a large internal ridge that does.

yes, ran them with filters and it runs exactly the same without.

 

[Jan_P]

I dont know much about carburetors but 2 -- .3 sizes up on jets sounds to much
Are we talking pilot jets as well as main jets.
perhaps go down on Pilot jets .And use clean ones

I once saw a man trying to kick start an old army motorcycle he kicked and kicked Full choke
Nothing besides him getting sweaty.
I told him to close the choke and he kicked and kicked but for every stroke 4- 6 the extra fuel was blown out and eventually it started and ran fine

 

[750triples]

I dont know much about carburetors but 2 -- .3 sizes up on jets sounds to much
Are we talking pilot jets as well as main jets.
perhaps go down on Pilot jets .And use clean ones

I once saw a man trying to kick start an old army motorcycle he kicked and kicked Full choke
Nothing besides him getting sweaty.
I told him to close the choke and he kicked and kicked but for every stroke 4- 6 the extra fuel was blown out and eventually it started and ran fine

I believe I went up 2 on pilot and 3 on main. I'll try downsizing and see what happens. Thanks to some suggestions from yall, I now have allen head screws on my carbs so rejetting is a lot faster.

 

[Jan_P]

Again I am not good at carburetors but if it was me I would leave the Main jets for now Jets that comes into action at high revs.
And go down to stock on pilot. 2 down --- might be to lean but for checking.

 

[750triples]

I installed the smallest pilots I have (one above stock) and the bike seems to start a little easier now? It’s hard to tell because it’s constantly giving me different results when I try something. Once the bike is started it runs at idle for about 30 seconds before dying out. After dying, it doesn’t start again unless I give it 5-10 mins.

 

[750triples]

It revs up really high on choke, around 5000rpm. If I try to give it any throttle it dies out.

 

[Jan_P]

It revs up really high on choke, around 5000rpm. If I try to give it any throttle it dies out.

I would check the charging Voltage and be sure it has enough power at ignition components
Then I believe it is still to Rich I would drop the pilot jet more

 

[750triples]

Sorry yall, I could’ve sworn I updated this post but here’s the rundown: downsized the pilot and main jet to one size above stock, needle at stock position. Mixture screws are turned out 1.5 turns. Runs perfectly.

The problem I was having with backfiring was because I was running it so rich there was fuel pooling up in the intake boots.