• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

V75 4 Valve - Misfire

R

rgakrill

Just got it firing!
Joined
Jun 7, 2009
Messages
24
Gents

I am just putting the finishing touches to a V75 4 Valve Tourer that i am building for my wife to tour round France this summer. It is fully restored and has a Spada fairing which looks smart. The French Blue paintwork takes a bit of getting used to but it was her decision,

I had a few issues with the Motoplat igniters (or so I thought) which was traced to a poor bullet connector leading to the coils. That explains why I have a spare now permanently wired up.

The thing is that the bike starts and runs well at sub 3000rpm but will not handle larger throttle openings. i have cleaned out the carbs countless times and replaced the 105 main jets with 118 as I am now running K&N filters.

When the misfire occurs you can pull out the choke lever and the bike runs fine (other than being obviously too rich).

I am convinced that it is a carb problem due to the way that the choke can overcome the misfire. It always occurs on the LHS cylinder despite swappinng the ignitors round and even substituting a spare into the equation. I've checked at the wiring again and again and there is a good spark on both cylinders, Could activating the choke overcome an ignition problem? If the problem was a poor spark then surely the bike would misfire whether it was running on or off choke?

We are off to France in two months and I am quickly running out of time to get the beast running.

Any ideas fellas (or girls)?

cheers

Richard Akrill
 

Attachments

  • New Image.JPG
    New Image.JPG
    361.4 KB · Views: 376
I have the motoplat on a Sessantacinque GT, very similar.

Do the coils check out OK? Have you swapped them?

I've noticed that the 'plat doesn't produce a great spark. If you have resistor caps, plugs or platinum/iridiums then it may be struggling. I'm using standard plugs now with 0.6mm gap and it is much happier. I have no resistance in the HT circuit. Put new plugs in as a matter of course. Make sure they have virtually no resistance.

Check the carby floats. I've had some phbh floats leak and fill with fuel. They can jam if the pivot pin isn't fully home or the float catches on the body.

Do you have both taps open and are they linked. Maybe the LH is getting starved. Check the gauzes and ensure no kinks.

Spray the LH intake manifold rubber and joins with WD 40 while the bike is idling. If the engine changes note you have an air leak.

118s? I run 110 mains with 40 pilots and I have foam filters and aftermarket mufflers that made lots of difference.

Just a few thoughts, no guaranteed answers.

Rod
 
You must log in or register to reply here.
Back
Top