Jump to content
IGNORED

Persistent left cylinder misfire


Go to solution Solved by Grim,

Recommended Posts

If you pull a plug wire and put a screwdriver in it, holding it close to a grounded surface, see if both sides throw the same, bright, strong spark.

  • Like 1
Link to post
Share on other sites
  • Replies 78
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Do it now while they can't come over . . .  

Oh, bugger. It's idling over 1000 on the tacho, haven't checked in GuzziDiag. Might have to go over this again.... Have I invented a new procedure, BTW? 😉   Thanks for all your help.

Hi Grim, I know I'm late to the party but FWIW my '02 Scura would backfire then spit off the RH inlet rubber after 100 miles. Replaced the inlet rubber & issue resolved, even found the low fu

5 minutes ago, docc said:

If you pull a plug wire and put a screwdriver in it, holding it close to a grounded surface, see if both sides throw the same, bright, strong spark.

Will do, it's starting to drive me mad.

Link to post
Share on other sites

This question is dumb , are both spark plugs NEW ? some older automobile garages have scopes and can measure the kV output of each wire . 

Link to post
Share on other sites
26 minutes ago, gstallons said:

This question is dumb , are both spark plugs NEW ? some older automobile garages have scopes and can measure the kV output of each wire . 

Yeah, brand new plugs. There's a small indy garage down the road, I could ask there.

Link to post
Share on other sites
2 hours ago, Grim said:

Will do, it's starting to drive me mad.

At least we know why you're mad. Some people are mad, and no one knows why . . . :blink:

  • Like 1
  • Haha 1
Link to post
Share on other sites
45 minutes ago, docc said:

At least we know why you're mad. Some people are mad, and no one knows why . . . :blink:

some people claim to be mad but have yet to be tested

  • Like 1
  • Haha 1
Link to post
Share on other sites
13 hours ago, Grim said:

Will do, it's starting to drive me mad.

By comparison, the XS650 is a reliable appliance. Alternator brushes every 15K or so and ride. As to Guzzi, I suspect that the company's products emerged from some sort of bizarre Fellini-esque drama-noir tale of death by slow descent into madness.

  • Like 1
  • Haha 1
Link to post
Share on other sites
1 hour ago, po18guy said:

By comparison, the XS650 is a reliable appliance. Alternator brushes every 15K or so and ride. As to Guzzi, I suspect that the company's products emerged from some sort of bizarre Fellini-esque drama-noir tale of death by slow descent into madness.

It's going to end up like a Giallo soon in the garage....

 

Yes, I have to invent my own problems with the XS... Like wouldn't it be somehow be better with Kawasaki Ninja carbs, or Honda CBR coils?

Link to post
Share on other sites

Ok... some things to note.
Both sparks are good and strong
But the left is definately rich at idle, sooty plug
Right plug is good.

I removed Meinhof's latest map, and wrote the standard map to the ECU. Surprisingly it  started running a little better.....

To get it to sync up last time I had ended up with the right air screw all the way in, the left about 3 1/2 turns out, which is not great.

I wound the left air screw all the way in, the revs dropped but so did the stumbling, I got a steady beat from the left hand pipe, but then the throttle body sync was miles off.

So the RIGHT cylinder is getting too much air, the air screw is all the way in but the vacuum is much lower than the left.

The following video shows (aside from a fool who is very bad at filming /motocycle diagnosis) the following point:

Standard map back on, both air screws fully closed.
Sync is off, right hand has less vacuum.

Winding the air screw out (alot) and can bring the TBs into sync.
This seems wrong, and the issue is the right hand side having too little vacuum?

Please excuse the home made mufflers, the nighbours were going to get pissed off at me if it went on much longer so I had to do something!
 


 

I guess the throttle butterflys are not aligned, or I have an air leak in the right.

 

I found aligning the butterflys difficult, the ball joint seems to want to go on all too easily, like it's not precise enough to ensure the plates are aligned.

I tried gstallons method of aligning the other end after removing the eclip, bit don't dare much better.

 

Link to post
Share on other sites

It will get easy after the 30th X. We give opinions and advice . It is up to you to diagnose and do the correct repairs . 

 Have a seat and evaluate what you think is the problem . 

  • Like 2
Link to post
Share on other sites

Back? Sooty? Rich or oil. Since you're already in there, and if compression is good, then you could swap injectors side-for-side and see if the trouble follows.

  • Like 1
Link to post
Share on other sites

# 1 for you benefit , run a compression test .  

# 2 are the intake boots in perfect shape ?

# 3 can you disconnect each fuel injector connector and see how much difference it makes on  the idle condition ?

 # 4 do you think swapping sides with the injectors will give you a difference ? 

 

 

 

 

 

 

3 3 

Link to post
Share on other sites
3 hours ago, gstallons said:

# 1 for you benefit , run a compression test .  

# 2 are the intake boots in perfect shape ?

# 3 can you disconnect each fuel injector connector and see how much difference it makes on  the idle condition ?

 # 4 do you think swapping sides with the injectors will give you a difference ? 

 

 

 

 

 

 

3 3 

 Thanks for you continued interest.

 

1. I will tomorrow, couldn't get a compression tester until then.

2. Left is, have another in the post from (kindly donated by Stewgnu) so soon the right will be.

3. I could, won't it just not run at all on that cylinder?

4. Right now, I don't *think* so. I am feeling like if the right is pulling more air and the screw is closed, then it would make sense that the butterfly was open more that the left at idle? I want to be in a position to open both air screws the same amount, therefore the right butterfly needs to close.  I think...

Link to post
Share on other sites
12 hours ago, Grim said:

It's going to end up like a Giallo soon in the garage....

 

Yes, I have to invent my own problems with the XS... Like wouldn't it be somehow be better with Kawasaki Ninja carbs, or Honda CBR coils?

just a little note here.... the XS will perform better with the earlier 38mm carbs. The ones from the '75 model are set up the best imo

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...