Backfires and lots of smoke coming out of 2nd cylinder

[Sebastian_99]

Hey guys,

I'm back with more newbie questions. And thanks for the help on the last issue (fuse box stuff). I now have my 79 XS11SF starting up ok but am encountering issues with the exhuast smoking really bad and backfires. The second cylinder has a lot of black buildup where the exhaust pipe leaves the block and when I look at the joints where the corresponding pipe goes into the other and the last joint I see it smoking bad. The smoke is gray (well, not black or super white). I also noticed the boots going from the carbs into the block looking pretty cracked. Is this all related to each other and if so what kind of diagnosis might one of you be able ot give me and tips on fixing it. I have the clymers manual so that will help me pulling anything apart (i just don't want to start digging into the wrong thing)!

Thanks again,
Sebastian

[Bonz]

So you are saying the pipes, or at least #2 is not sealed and exhaust is escaping to leave black residue and visible smoke along the way out the back, correct?

The exhaust system in and of itself needs to be solid, i.e., no leaks in my opinion to get other stuff in line. What condition are the carbs? Cracked boots are the norm, as long as they don't go all the way through you are fine. You can "fix" them with plasti dip, I used the spray. Do a search and you can read about it. I did mine and they look a lot better.

You can do a compression check on each cylinder to see what condition you may have internally to the top end.

What time are you around in the afternoon, I can swing by tomorrow to lend a look-see if you want. Let me know.

[Sebastian_99]

I haven't gotten into the carbs just yet. Before I got the bike I did a compression test and all was well. I have a buddy coming over sometime tomorrow early in the afternoon, we are going to take a look at the exhaust and try and pinpoint the problem. I'll let ya know if I can't figure it out.

[bikerphil]

Maybe run some seafoam fuel treatment.

[skids]

I haven't gotten into the carbs just yet. Before I got the bike I did a compression test and all was well. I have a buddy coming over sometime tomorrow early in the afternoon, we are going to take a look at the exhaust and try and pinpoint the problem. I'll let ya know if I can't figure it out.

You are going about it the right way. Get your exhaust fixed up and the intake boots also THEN carbs, you you will be chasing your tail. The weld location on specials under the heat shields (by the foot pegs) is a common location for cracks, so you might want to take a look there also.

[Sebastian_99]

That's exactly where it starts smoking.

[Bonz]

If the exhaust has a crack at the weld, you are pretty much gonna need to get it re-welded or get a coupler to join each side of the break and put a clamp around it.

Sebastian, I took my 80G exhaust to Muffler Masters here in Colorado Springs and they fixed up the system. The main work was to graft on Harley Sportster mufflers to replace the rusted out back ends of the existing muffs, and they rewelded the break at the same spot you have.

[LoHo]

Try to figure out if it is exhaust (which will come out with some force), or just burning oil and crud that burns as it heats up and smokes in lazy strands. A good cleaning will often reveal interesting details about a new bike.

[Sebastian_99]

I had a friend come over the other day and we simply pulled that pipe out and reseated it and bolt that sucker back down and now I'm not getting the smoke. It was weird but I can't say I am complaining, easy fixes are my favorite.

[TopCatGr58]

Sebastian,

These engines use CRUSH Washer style exhaust gaskets, and with years of pressure and heat, they get crushed and hardened to where it can be difficult to get a good seal. And the gaskets are hard to see and differentiate from the head because they are metal/fiber sandwiches and turn the same color as the head....will look like a lip inside the head port and not necessarily fall out when the pipe is pulled. I've had to take a screwdriver and drive it across the hole to get it to wedge behind the gasket to then be able to pry it out. Replacements are relatively cheap...~$4.00 ea, several places to get...local dealer, ebay, partsnmore.com .

T.C.

[BradW87]

cracked boots

Mine has some cpracked boots as well, previous owner did a bad job at sealing them. I thought I had to replace them. Is there a no return point with cracked boots? Or can you use the plastic dip even lightly cracked all the way through?? Also having some major issues with my current 79 de standard. Have details in my visitor message if anyone would be willing to help a guy out still green in the gills. Much ablidged!

[TopCatGr58]

Hey Brad,

As I think you've found/read, the intake boots are double walled, so after a good inspection of the inner tube if found intact, then feel free to slather whatever sealant you want to get them looking like what you want. Folks have reported having to apply like 10 layers of spray on plastidip or equavilent to get them to look decently smooth on the outside. Others have applied RTV, but it's a bit more difficult to get it to look smooth when applying it, YMMV.

The other things with the boots is of course to take them off the engine to apply the sealant. This way you can inspect the MATING/Sealing surface, it comes with a thin layer of rubber over the metal plate, but it also often deteriorates, hardens, breaks down, crumbles, etc., and so you can get vacuum leaks! Brushing off the boot surface to remove the old rubber, and then apply a non-hardening type sealant like Yamabond, Threebond, Permatex, etc., some also recommend a gasket, but I feel it seals fine with just the sealant alone. The Synch port caps can also harden and even though they are ON the port tube, they can actually be loose and also cause a vac. leak, so inspection and replace if hard/loosened.

T.C.