bogging down when hot

[sargas3]

I have a 79 xs 1100 special all stock, it runs good but at times it seems to bog down an feels like it has a lot less power. It seems to be when its hot out and I’ve been driving for awhile. It get going and it will feel like im in a gear to high. im wondering if the mufflers since they have 33,000 miles on them might be clogged up and the air flow is off. Or if you guys might have some ideas.

Would also like to replace the mufflers. the header is in nice shape so was wondering if anyone has a recommendation for mufflers that will perform better than the stock and maybe a little healthier sound. I don’t want them ridiculous but a little healthily rumble would be nice. Thank you for your advice!

[sargas3]

one more question. as this is a stock bike I don’t thinking getting the full power put of the 1100cc it has. I want to be able to ride along side my brother with his r6 but currently I feel under powered. Are there any simple things I should do to improve performance. I did get a k&n filter new ngk wires and plugs and changed all the fluids but id like to get the most out of this bike. I’m one a budget but I will save if I need too. thank again for your advice!!!

[DiverRay]

I would start with the tech tips on the left side of the page. The loosing power when hot may be the carbs, as they are the one item that can make or break the way this bike runs.
If you have not done so, go on a run, stop and pull all 4 plugs when warm. look at the color on the tips, they should be light tan or brown. If they are white, you are running lean, and black, you are running rich. This would be your starting point. Once you know how the bike is running, then you can do a search with carb and rich or lean as key words.
There are a couple of threads on mufflers. Some people have gone to stock HD mufflers, as they are cheap. Most HD riders take them off, so you should be able to get a nice pair for a small amount of money.
Ray

[sargas3]

thank you Ray. ive been readin the differant tips and such in that section. im really hopeing i dont have to touch the carb. I have tried working on carbs before on cars and have never been able to get them right. I do ok with other stuff but carbs scary me. and its harder to replace this carb than a cars. are there any upgrades that are a must for this bike? Ie had it for 2 years and havent changed a thing yet. thanks again!

[DiverRay]

Well, you should buy a "carb stick" or vacum gauges and sync the carbs. That is #2, #1 would be to run a can of "Seafoam" or "Berryman's B12 Chemtool" through the fuel system. I would get a pint can, and add to a half empty tank. Run it down to the light, and then fill with gas once again. That may help the problem without going into the carbs.
You probably NEED to have the carbs synched, once they are clean. It isn't very hard, and the tech tips will help a lot. The tool to do it will be paided for after one use, as most shops don't do a good job, and charge over $100. Don't forget to put a fan in front of the bike when you work on it. You need to keep air flowing over the engine as you run it.
Ray

[sargas3]

ill try both. the have read through the teck tip and i think i can do it. so ill see if i can get the tool and the Seafoam or "Berryman's B12 Chemtool. the wife works at a bike shop so if its sold there I can get a break on it. thanks for the tips i could use all the help i can get!

[randy]

Sargas3;

When it bogs, does it feel like it's running on 2 cylinders? That may be the pickup wires.

Or, like others said, could be fuel related (lean) condition.

If the bogging is accompanied by pinging, check your ignition timing, could be advanced too far.

[sargas3]

no pinging, but yes it does feel like its a cyl or 2 short! its not all the time and there has been hot days that it didnt happen. ill try and see if there is a short in those wires too. thank you!

[randy]

Not a short, but a break. Look up the fix in the tech tips.

[sargas3]

reading through it now. ill try that as soon as i get off work today!

[DiverRay]

Sargas3,
Check the FRONT pickup wires. They go through a "clamp" that is the break point for most of the problems. The fix is easy if done correctly the first time. I also loosen up the clamp point, so the wires will slide back and forth easily. That was the fix I sent to Yamaha back in '78 when I worked on these...
Ray

[TopCatGr58]

Hey Sargas,

Good tips here, but another thing would be to just turn the petcocks to PRIME when it starts to bog. Could be a faulty Octopus, and when running for a while, might not be getting enough vacuum to open the valve completely, and you could be running low on fuel in the bowls!?

Also, pop the gas cap loose, there's a vent in the cap that can also get clogged and prevent the flow of fuel due to vacuum lock in the tank!?

Also, with the K&N filter, and then going to other mufflers, you may be in need of a rejet a couple of sizes larger, again READ YOUR PLUGS and adjust accordingly!

Also, check your intake manifolds for vacuum leaks, along with your vacuum hoses, including your vacuum advance hose!
T.C.

[sargas3]

ok checked the pickup wires for breaks. I let it run for awhile then tugged on them with no differance in the idle. looked for vacumme line leaks but didnt find any yet. then it started raining so i didnt get much else done yet. it looks like rain all doy today so I may not be able to work on it agin till tomarrow. =[

[yamarider]

I am going to side with TopCat. I was riding the other day in hot conditions (95 degrees) cruising at 70mph when the XS started to sputter. Putting the fuel petcocks on reserve solved the problem. I know that I wasn't low on fuel - had just filled up 30 miles prior. It has done this before in hot conditions, so that whole vacuum lock theory makes sense to me. As a rule of thumb, I don't ride long distance above 90 degrees, but had to in this instance.

[sargas3]

thats really interesting! im going to try that. its been hot up here in michigan when it hasnt been raining. so my choices are a car with no are or my bike. Im taking that bike!!! every chance i get! its been raining for 2 days though so im a little bummed. i want to work on it and ride again. do these bikes have a fuel filter?