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Popping/backfiring?

milestones54
honda305.com Member
Posts: 3
Joined: Sat Apr 07, 2012 8:14 pm
Location: Sydney, Australia

Popping/backfiring?

Post by milestones54 » Sat Apr 07, 2012 8:19 pm

Hi all

Picked up my first bike this week, little CB72 in pretty good nick.
A whole lot of a fun and gets a lot of attention

A problem is bothering me however. The bike is backfiring after about 10-20 minutes of riding. It will pop/backfire even when the clutch is in or is in neutral (rather than deceleration) and I'm not quite sure of the cause.

I'm sure this is simple but I'd love to get a few opinions before I start attacking the problem
Last edited by milestones54 on Sun Apr 08, 2012 9:38 pm, edited 1 time in total.

milestones54
honda305.com Member
Posts: 3
Joined: Sat Apr 07, 2012 8:14 pm
Location: Sydney, Australia

Post by milestones54 » Sun Apr 08, 2012 9:35 pm

I'll also add that the bike idles slowely higher as it heats up (I had it idling at maybe 3700 today)

Kirk
honda305.com Member
Posts: 71
Joined: Sun Jul 08, 2007 5:47 pm
Location: Portland Oregon

Post by Kirk » Mon Apr 09, 2012 8:23 pm

Welcome to the site. I will throw in my two cents, had the same issue with a cb350. Turned out to be a timing issue and rusty gas tank fouling the carbs. Also had a loose muffler.

Try the search function there are a lot of posts such as this one.

http://www.honda305.com/forums/right-si ... t=backfire

You might also add your location to your profile , someone close to you may be able to help you out or give you more guidance.

Also try Ed Moore's tuning recipe located here.

http://www.honda305.com/cb77_700/cb77-716.htm

Thanks,
Kirk
2-1966 CB77 Projects
1965 CB77 Partsbike
1967 scrambler pile of parts
1972 Cb350

Jlovvorn
honda305.com Member
Posts: 477
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Post by Jlovvorn » Tue Apr 10, 2012 11:17 am

Check the play in your points cam now, before you spend three months chasing your own tail like I did.

See "Superhawk from Hell" etc, etc.

rzgkane
honda305.com Member
Posts: 537
Joined: Sun Feb 12, 2012 11:12 pm
Location: Huntington Beach, CA

Post by rzgkane » Tue Apr 10, 2012 11:37 am

Have you confirmed excessive play in the advancer?
Jlovvorn wrote:Check the play in your points cam now, before you spend three months chasing your own tail like I did.

See "Superhawk from Hell" etc, etc.

Jlovvorn
honda305.com Member
Posts: 477
Joined: Tue Dec 27, 2011 11:10 am
Location: Washington DC

Post by Jlovvorn » Tue Apr 10, 2012 11:59 am

I have confirmed too much play at the cam.

Parts are still coming in. Pulling engine this weekend.

I wanted to have cam bearings, chain, tensioner gasket, new tensioner, and some other stuff all at the ready before pulling the engine.

Having studied the operation of the spare head I ordered off EBay - which has the exact same can play and visibly loose springs - I feel confident mine needs fixing.

rzgkane
honda305.com Member
Posts: 537
Joined: Sun Feb 12, 2012 11:12 pm
Location: Huntington Beach, CA

Post by rzgkane » Tue Apr 10, 2012 12:02 pm

Please take many pics and post them for all of us to learn from. Good luck.

Where did you get the new bearings, chain and tensioner?
Jlovvorn wrote:I have confirmed too much play at the cam.

Parts are still coming in. Pulling engine this weekend.

I wanted to have cam bearings, chain, tensioner gasket, new tensioner, and some other stuff all at the ready before pulling the engine.

Having studied the operation of the spare head I ordered off EBay - which has the exact same can play and visibly loose springs - I feel confident mine needs fixing.

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