Can't seems to find an answer to this.

[Johan Dubs]

Hey guys,

I bet this has been answered somewhere on here but I can't seem to find it.

I've been noticing something going on when I've been riding the bike for awhile and it's all good and warmed up. A lot of times when I come to a light and put the bike in neutral I like to do quick little rev's (A habit I gained from dirt bike racing ). I have noticed that every once in awhile I'll hear what sounds similar to a backfire of some sort.... but it is coming from what sounds like the airbox/carb area of the bike. The bike rev's fine and everything while doing it, I just notice it making this noise sometimes.

I am assuming it's in the carbs somewhere. I'm just not familiar enough with this sort of set-up to know.

Any thoughts?

I'm sure I will get the "you need to thoroughly go though your carbs response" which I will be doing this winter. Just curious as to why this is happening and if it's something to be worried about.


Any help is well appreciated.

[BassCliff]

Hi,

What maintenance, repairs, or adjustments have you done to your bike? It could be caused by any one or more of several things.


Thank you for your indulgence,

BassCliff

[Johan Dubs]

Thanks for getting back to me BassCliff,

Well I bought the bike about two months ago. Since I've bought the bike I have really done much to the engine/carbs besides:

-new plugs (correctly gapped)
-new sparkplug wires
-new air filter/ lightly oiled like I've read

Other then those few things I personally have not gotten the time to run through the carbs as of yet. (I will be this winter) The man I purchased the bike from said he went through the carbs and cleaned them, which I have no reason to doubt. I do, however, doubt he did it thoroughly and replaced all the o-rings like is recommended.

Besides those few small things I did I've replaced the front master cylinder, put a stainless brake line in, a new rear caliper, new pads, and replaced the clutch cable with close care to properly adjust it.
I did attempt to take a look at the chain but didn't really know what to do. There isn't an excess amount of slack so I just cleaned and lubed it like my dirtbikes. I was hoping for a master link to take it off and inspect closer, but no such luck.

[d19407]

You mentioned that you replaced the air filter. Check the air filter is seated correctly and that the box is 100% sealed. I used some weather stripping from Home Depot.

May I also recommend checking the metal clamps that secure the carbs to the intake boots and the metal clamps that secure the carbs to the air box. ? These items may have loosened a little when you fitted the air filter, allowing a little bit of air to get in to the system.

Many more experienced folks have previously mentioned how important it is to make sure the system is free from air leaks and I can only confirm from my own personal experience how critical this is.

[bwringer]

Backfires are usually caused by air leaks in the intake system or the exhaust system.

[Steve]

I know it's not as much "fun", but stop revving the engine while you are stopped.

If the noise only happens when you do that, don't do it.

.

[dueller]

Welcome fellow Michigander! Did my carbs this spring as was needing to use a shot of ether to get it to start this year. Big difference. Hope you can get to this this winter!

[Johan Dubs]

Alright so I just got back from the garage.

In response to d19407 and swringer:

First thing I did was check for any leaks anywhere... so I took the gas tank of to get a good view of everything. The first thing I noticed was a hose coming off of the top of the airbox.



The hose went up to the top valve cover.



It was pretty much just sitting on the port it was supposed to connect to, so I took care of it!



Next I moved onto the clamps around the carbs. The clamps between the carb and airbox all got tightened. They were all somewhat tight, but not to my standards . After that I moved to the side between the carb and engine. These were already tightened down as much as they could be tightened. Personally I don't think they are leaking, but if I do put a little effort into it I can get the clamps to spin a little.

I also looked at the airbox itself. The only thing that seemed to be a problem is the lid itself. First off it doesn't seem to sit very well on the top of the airbox. It tilts back and forth like an off balance table. Making matters better, there isn't any weather stripping to be heard of on the bottom side.



Probably needs to be taken care of asap. Tomorrow I should get that done, just need to buy some weathe rstripping for myself.

While I was at that I decided to check the plugs and electrical system. The plugs looked alright to me, but I took pictures of them if any of you want to see them. The charging system also seemed to be in good order. With the bike on but not running I read about 12.7 volts. At idle I read about 13.4 volts, and when at 4500ish rpm I read 14.7 volts. Seems to be alright, but inform me if I am mistaken.

Steve: I like the way you think. I'll try my hardest!
Dueller: Maybe we should get a group of Michigander GS riders and do a tour one weekend? I think that would be pretty sick.

I really appreciate everyones help.

[JEEPRUSTY]

Be carfeul when trying to cinch up a seal by tightening.
Old and hard things will not compress much and you will end up breaking things and not really improving the seal.

People strip their valve cover bolt holes all the time doing this.

My vent tubes were torn as well. I had too order one new one cause it was a formed tube that was too difficult to replace with stnadard tubing.

[Johan Dubs]

Just another update. I rode the bike into work just now. It actually felt noticeably smoother at speed. I would like to attribute this to the hose that I fixed.... could just be placebo effect though.

Be carfeul when trying to cinch up a seal by tightening.
Old and hard things will not compress much and you will end up breaking things and not really improving the seal

.

I tried to make sure I didn't make them too tight. I just made them more snug. I personally know that I have a problem with over tightening bolts and such. I try not to overdo things anymore.

[dueller]

Yeah a ride would be cool. I have to sort a couple things out on mine and I would be game. Gotta do it soon though! There were a few guys that went down to the vintage bike show out around Battlecreek a month or so ago. Yeah. that breather hose probably wasn't helping your situation out any so good catch there!

[Johan Dubs]

More info if anyone is interested:

I took apart a couple things the past few days.

I replaced the petcock with a brand new OEM petcock and replaced the vacuum line attached to it. I looked at the electrical system for a second time. Charging all seemed good as it did last time. I found that the R/R was brand new, the coils were brand new, and the wire/plugs were brand new. The PO also told me he replaced the stater and I have no reason to doubt him after all of these parts were new like he said. I sealed up the air box with some weatherstripping. I did notice coming off of the bottom of the plastic portion of the airbox was port without anything attached to it. It appears to only be a drain port. Adjusted my clutch again and then I changed the oil for the hell of it. I used 15w30 diesel motor oil from Rotella.

Started the bike up....no leaks.....level is good.... take it for quick spin. Clutch felt amazing. Better than before I must say.

The only other thing I did notice was that the crossover on the exhaust was leaking. Which I am going to go ahead and believe is causing an issue.

Any thoughts? I didn't take it out to see if it fixed the problem or anything. Just wondering if anyone has thoughts pertaining to the exhaust causing issues.