Hello,
I have a problem with my XTZ 750 from 1994. Hard starts, backfire to exhaust black spark plugs . Cant hold idle ,can't go past certain rpm (3000-4000)
Things i do :
Changed spark plugs (2 times) . Clean and rebuild carbs , tried TCI in another XTZ , changed ignition coil , spark plug caps, measured pick up coil resistance , checked wiring , tried running without rectifier (sometimes it can cause interference to TCI ) .
my last hope is checking stator and picup coil or engine timing .
I'm already desperate, and that's why I'm turning to you.
Thank you very much for any help .
https://youtube.com/shorts/FiXXr8cGd78?feature=share
XTZ 750 misfire?
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Hawk
- On the ladder
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- Joined: Mon Jan 25, 2021 10:48 am
- What Bike or Bikes Do You Own?: Super Ten :)
- Location: UK
Re: XTZ 750 misfire?
Are black plugs dry or wet?
Assuming dry and sooty it may indicate running rich. Did you check the jets when you looked ar carbs?
Also try running up without air filter and see if that makes a difference.
And lastly check choke is not stuck open.
Good luck
Assuming dry and sooty it may indicate running rich. Did you check the jets when you looked ar carbs?
Also try running up without air filter and see if that makes a difference.
And lastly check choke is not stuck open.
Good luck
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clARky
- On the ladder
- Posts: 58
- Joined: Sat Apr 24, 2021 6:55 am
- What Bike or Bikes Do You Own?: 1990 Yamaha XTZ 750;1971 Triumph Bonneville T120R;1973Triumph TR5T;1997 Suzuki DR 350 sev; 1938 Norton Model WD16H
- Previously Owned Bikes: 2015 Triumph 900 Scrambler ,1991Yamaha XTZ 750; Yamaha FZR100; Honda VFR 750FM ;1989 Kawasaki GT750; Honda CRM250 AR; 1997 Cagiva Gran Canyon; Yamaha DT 175;Honda CX500 ( X5);Puch 3.
- Location: UK
Re: XTZ 750 misfire?
Don't make the mistake of thinking too far down the line and going ignition timing.It sounds like fuel issue. Check levels again first, then possible sparkplug failure dueto overfuelling.
I couldn't understand why new NGK plugs were failing and had a similar scenario.Misfire,backfire and blackish exhaust smoke ( running rich where it wasn't ignited).
After a discussion on a forum I discovered from someone who spoke to an NGK rep who told him that they no longer seal the ceramic part of the plug just below the thread ( or maybe all of it).The reason being that modern fuel injected engines do not overfuel .However, on carburated vehicles contamination from oil or fuel can affect the plugs ability as the ceramic part soaks in the contaminants.
I also found that the problem was with the carbs even though I had rebuilt them.A mechanic friend who worked in a race shop had them off and inspected them and found a problem with the needlejets in each carb ( at least that's what I think he said) and had replacements at hand.
Suffice to say the problem was cured.
Hope this helps.
I couldn't understand why new NGK plugs were failing and had a similar scenario.Misfire,backfire and blackish exhaust smoke ( running rich where it wasn't ignited).
After a discussion on a forum I discovered from someone who spoke to an NGK rep who told him that they no longer seal the ceramic part of the plug just below the thread ( or maybe all of it).The reason being that modern fuel injected engines do not overfuel .However, on carburated vehicles contamination from oil or fuel can affect the plugs ability as the ceramic part soaks in the contaminants.
I also found that the problem was with the carbs even though I had rebuilt them.A mechanic friend who worked in a race shop had them off and inspected them and found a problem with the needlejets in each carb ( at least that's what I think he said) and had replacements at hand.
Suffice to say the problem was cured.
Hope this helps.