Hello! I'm new here and have minor tuning issues :)

Hello,

I am a new motorcyclist (been riding for a few months now) from Albuquerque NM, and bought a 1981 XJ550 seca for $700 from craigslist. The bike is fun as hell and fulfills my dreams of owning a sportbike to some extent. I've also been lurking your site anonymously for a few months now, and have been simply eating up your advice.

To fill you in, my bike has had continual issues: leaking oil pan, dirty/unadjusted chain, poor idle, starting issues, an EXTREMELY DIRTY CARB, a cracked and leaky air box, leaking valve cam cover seal, an ignition switch that mysteriously died, loose battery cables, and low brake fluid levels. This thing has died and left me stranded on at least four to five separate occasions around the city.

Let me tell you that I'm now not only a beginning motorcyclist, but a beginning motorcycle mechanic! ARGGGHH!!! The good news is that all of these issues have now been solved, except for replacing the valve cam cover seal that hardly leaks oil at all... I really have this website to thank for all of the solutions I've found. For example, many of the carb cleaning tutorials you guys made allowed me to DISCOVER THE ENRICHMENT CIRCUIT, the joys of avoiding spraying carb cleaner in your eyes, and what float levels should be. My newly-bought Clymers manual had zero documentation for the enrichment circuit and its float level instructions mislead me to set all of my float levels 1-3mm below the physical top of the float bowls instead of 1-3mm below the screw heads that bolt it on. This caused me to run extremely rich for a long time, which eventually carbon coated my plugs.

I've replaced the oil pan, coated my air box in copper tape (the only thing that has worked because even oil/gas resistant plastic glue refused to hold), TWICE cleaned my carbs which were gunked up and clogged due to silicon gel glue that the previous owner used to seal up the air box getting sucked into carburetors , and put a lot of work into the bike.

The only thing that remains is to tune the machine, which according to you guys requires: setting valve shims, changing the air filter, checking intake tube seals, replacing/gapping the spark plugs, bench syncing the carbs, using a colortune plug to set idle air screws, and pressure syncing the butterfly linking screws. This seems very straight forward except that I'm a poor student and will likely only be able to buy a colortune plug, while not affording the $80+ valve shim tool from Yamaha. I've already bought new plugs and an air filter, and a friend of mine has a 4-meter pressure sync setup that I can borrow.

I heard from a friend that you can use a screwdriver instead of the valve shim tool. Is this true? Will I need to do a compression test as well, and if I do, is there a cheap way to do it?

Oh.. one last thing... nearly all of my rubber carb diaphragms have a few small holes in them. I just did a price check for these online, and they look to cost $80 a piece Would you guys recommend if I used a soldering iron to melt o-ring rubber into the diaphragm rubber? I need something cheap that will work, a real McGuyver job if you catch my drift! Assuming that I get both rubbers to melt into each other, I think there will be sufficient mechanical strength to hold it all together. What do you guys think?

Anyways, I'm glad to now be a part of the community. All the work you guys have already done has helped me more than you could possibly know. Thank you!

 

Check your rear brake for lamination. Better yet, just replace it! Fitz will be along some time to reinforce XD.

Sorry cant help with pretty much any of your problems, but I'm pretty sure you can use a layer of silicone on the outside to seal up the boots instead of melting rubber into them...

 

Ternk; there's no $80 valve tool. The "valve shim tool" costs between $12-$15 everywhere, ok maybe $20.

You can use liquid electrical tape on the intake manifolds, wrap them with bicycle inner tube, or pack the cracks with black high temp silicone RTV (my preferred method.)

If you've got access to a 4-stick manometer, all you need is the colortune and a YICS shutoff tool for the carbs; and the aforementioned inexpensive valve shim tool and you're good to go for special tools.

You can use the alternative method of shoving a zip tie or piece of insulated wire down the spark plug hole to keep the valve down and not even need the shim tool. Personally, I don't advocate this practice; others find it easier than using the tool itself.

And that's DElamination, Pseudonym, and yes he should, and right away.

 

Okay, so it looks like I'm buying a new rear brake pads. I've read up on your site, and it seems like a common recommendation so that people don't get killed should old brakes cause a rear-tire lockup.

I should probably put some RTV or oil/gas resistant sealant on the top surface of my diaphragm rubber?

Thanks for the advice. I could've sworn that the valve tool was a lot more expensive. I'll be working on it throughout the week and the weekend, and I'll let you guys know my progression

 

The Yamaha tool probably is that expensive - PM Chacal he has them cheap and has most parts about as cheap as you will find.

A little RTV on the diaphragms should be fine

 

Liquid Electrical Tape on the diaphragms - - RTV might peel with time.
I wouldn't try to melt rubber onto them.

You don't need to bench-sync carbs on a running bike. do a running sync after the valve adjustments. I use the 12/2 wire valve "tool"

Stuff the YICS passage with knotted, oil soaked rag strips- - will save you $35 for now. No real need to make or buy the tool right away.

And welcome to XJBikes!! Tell us how your tune-up goes.

 

Sorry; yes liquid electrical tape for diaphragms; black high-temp RTV for carb intake boots.

You can check your float levels on the bike too if you can prop it up enough in the front to get the carbs level.

 

I've had really good experiences using a bent tie wrap instead of the valve shim tool (if you short on the money you really don't need to get it). You can look on here and find posts on how it is done. I'm guessing its exactly like the insulated wire thing but it seems a bit easyer to me as you might not have insulated wire of a thick enough gauge hanging around.

 

Oh hell yea. Such good advice. Looks like I'll be able to get to her this weekend and will be reading up on the bent zip/wire tie method. The oil-soaked rag is a good idea, too.

thanks guys

 

Make sure you have a rod you can pass through the YICS port. The rag pieces do work but are a royal pain to get in and out.

 

Anyone ever try putting o-rings on a 3/8th dowel (I dont know if thats the right size or not for sure) with a good supply of high temp grease as a ycis tool?

 

I actually like the rubber hose with a Schrader valve clamped-on idea.
Just need to get the perfect size Neoprene heatproof hose, add 20 PSI or so, done deal.

 

Good luck with that. Let us all in on it if you find something that won't melt from contact with uber hot surfaces.

 

Skycraft Surplus in Orlando- - lots of NASA stuff just laying around. I'll ask. Did anyone ever get a good heat reading of the YICS passage??

One man's Space Junk is another man's treasure.

 

Hmmm, I removed my carbs to further set the float levels to EXACTLY where they need to be and to put liquid electrical tape on the small holes on the diaphragms.

Well.... those holes are where the rubber has bends when the diaphragm plunges up and down. It so happened that I put too much on those areas, because I STRONGLY suspect that the liquid electrical tape has made the rubber so thick that it is making it hard for the carb pistons to move up and down, which in turns makes the bike tend to refuse to drop in idle during driving and erratic idle speeds that don't want to drop down.

My hope is that tonight I will clean the liquid electrical tape off and put only a VERY small amount to seal the holes, yet still maintain suppleness. I'm not exactly sure how easy it will be to remove the stuff, but I'll let you all know how it goes.

In the meantime, I've contacted chacal to order some valve cover screw "donuts", a valve cover gasket, a YICS cutoff tool, and a metric feeler gauge if he's got one. I'm helping a bud first-time clean his carbs on an old GS500 suzuki this weekend, and will be checking my valve clearances at the same time, so it sounds like a fun weekend for sure.

I'll keep you guys filled in on the progress

 

By the way, all of my carb pistons pass the clunk test with flying colors.

 

look at you never wrenched on a bike now your helping a buddy wrench in his Great Job

 

Hmmm, I put too much liquid electrical tape on the small carb diaphragm holes the first time through. It caused the bike to have very erratic idle, anything from 4-5k all the way down to stalling out at 1,100 rpm; the idle would also hang up high, unless I let out my clutch in 1st gear at stops to bring it back down.

So, I removed that liquid electrical tape, then put on VERY small amounts to just cover the diaphragm holes, and I'm still having the same problem

Another thing that I did is change most of my float bowl levels, which were all 1 - 4mm too high. Perhaps this is causing problems, as well.

I am considering buying new carb throttle shaft seals and possibly replacing my enrichment circuit seals as well, since it could be a leaky enrichment circuit causing my problems. Perhaps I should set all of my idle mixture screws out to the standard 1.5 turns (or was it 2.5 turns???). I doubt that such miss-matched idle screw settings would cause idle to hang however, but a leaking enrichment circuit might do that.

This bike makes me want to rip my hair out!!!! Anyways, if Chacal is reading, I'll order the valve checking parts ASAP. I've just been very busy both at work and when I get home.

 

I did some WD40 spray, and I think that my idling problem is a vacuum leak on either the 3rd or 4th cylinder intake. One day my bike will run well.... I applied some black high-temp RTV sealant on them and will know tomorrow morn if it works. Any advice you guys can give would be great.

 

Make sure all your screws are tight on the boots (both airbox and mainfold side). Usually a hang means an air leak somewhere, and if it's hanging that high, something ain't right.

Hope it works out!