Bike backfires and pops during start up

[Quilty]

That ks for the input skull. When I took the 76/77 carbs off to put the 74/5s on I noticed that the brass fitting on the fuel crossover tube on one of the carbs was loose and was only held in by the rubber tube could have been causing the air leak. Anyway for now I'm happy with the 75s im close to tuning her. Did you ever get to the bottom of that peanut I wish I had your patience

 

[peanut]

Hi Quilty . I'm not sure why Skull650 posted that link ? I can't see what relevance it has to your particualr problem but he must see something I'm missing
Unfortunately I still have not identified or cured my hanging idle problem.

Funny you should mention the loose brass fuel link spigot because when I took my carbs apart last week one of my tubes fell out as well !.....

I just pushed it back in without thinking but maybe I should have cemented it in .
When the tube was removed I looked inside the hole on the carb body and discovered that the hole into the fuel bowl was completely blocked off with hard crud . ! I'd never have thought to look through that spigot if it hadn't have fallen out .

 

[650Skull]

Quilty, Yamabond is not necessary on any part of the carbs. Any gasket on the carb will seal well with an, even, thin layer of grease on both sides and it also means they are easy to remove and can be reused without any bother as long as they don't get damaged when removing.

Any loose fittings need to be reattached properly to stop any leaks.

If the 533 carbs have the same needle and needle-jet as the 74/75 carbs then i don't see why the main is different but starting from the sizes recommended for that carb would be where i would start. Sometimes it is best to reset everything back to manual specks then start over again with another clean with carb cleaner and compressed air.

Let us know how or when you get it sorted to finish the thread for others

 

[peanut]

Threebond is an excellent liquid gasket cement which is a close formula to the original Yamabond .

I'd recommend to use it wherever you need to use it . When you are putting parts back together that are 35+ years old with thin poor mating surfaces, threebond will seal many minor imperfections well ,particularly around areas like the cam chain tunnel and cylinder head stud holes etc. Everyone with any sense uses it where its needed to avoid air and oil leaks..you cannot cause any harm by using it .
I'm happy to say that I have not had a single weep or leak anywhere on my engine due mainly to the judicious use of threebond.

it will be a pita to remove as will many gaskets but most folk don't tend to strip their engines every other week

 

[650Skull]

You recommended putting Yamabond on the carbs. Yes use it on the engine but not on carbs or the inlet manifold gaskets.

Engines do not usually come apart very often but carbs are often taken off the bike and apart. Yamabond is not necessary in this area

 

[peanut]

You recommended putting Yamabond on the carbs. Yes use it on the engine but not on carbs or the inlet manifold gaskets.

Engines do not usually come apart very often but carbs are often taken off the bike and apart. Yamabond is not necessary in this area

well it would seem that we differ in opinion on the use of Threebond

I'm sure most sensible people will make up their own minds about when and where to use a liquid gasket .

However this is neither the time nor place to discuss the merits of liquid gasket application so perhaps you should consider sticking to the topic and try and offer some useful advice to Quilty to cure his backfiring problem

 

[Quilty]

Get a room lads. Preferably a sound proof one. Haha I agree and disagree with both views since I put the liquid gasket between the carb and gasket not the engine /gasket side after using wet and dry paper on all relevant surfaces. I can be reasonably sure that there are no air leaks there. Since those particular gaskets are as cheap as chips it doesn't make sense to reuse them. The 74/5 carbs are 0 mileage which means new. I was just lucky to come across an old yamaha dealer who had them sent to him as spare in the 70s. I will look in depth at the 76/77 carbs but I think they need a rebuild. The new carbs have cured all sorts of problems including the hanging idle that peanut was experiencing on his I will rip into the 76/77s this weekend and post my findings

 

[650Skull]

Dress the stubs flat on wet and dry then refit both the stubs and the rubber inlets with new gaskets and some yambond liquid gasket to both sides of the gaskets .
From this point on you can disregard these and be reasonably certain that its unlikely there would be an air leak on either of the inlets .

Next I would check both carbs for cracks holes splits and missing plugs ,bungs and parts that could cause an air leak. I would remove both choke bodies/assemblies and renew their gaskets or apply a little Yambond .Even a slight air leak here would make it impossible to get a stable idle or easy starting.

You recommended putting Yamabond on the carbs. Yes use it on the engine but not on carbs or the inlet manifold gaskets.

Engines do not usually come apart very often but carbs are often taken off the bike and apart. Yamabond is not necessary in this area

well it would seem that we differ in opinion on the use of Threebond

I'm sure most sensible people will make up their own minds about when and where to use a liquid gasket .

However this is neither the time nor place to discuss the merits of liquid gasket application so perhaps you should consider sticking to the topic and try and offer some useful advice to Quilty to cure his backfiring problem

When you can fix your carbs i will take your advice

 

[peanut]

come on Skull you are starting to act like a complete arse

You are hyjacking another members thread to upload previous posts of mine to have a dig at me .

if you want to spend your time searching through all my previous posts in order to have a dig at me at least have the common decency (and the balls) to start your own hate thread or something.

this vendetta is simply making you look like a first class idiot.