Bike idles fine but will not rev

Now that's funny riiaght theare!

I started pulling the left hand side cover off the engine. The round cover, about 6 inches in diameter, that seems to be centered around the crankshaft. As I loosened the 4 bolts about a 2 quarts of oil poured out. Please, please please tell me there is supposed to be oil inside that cover. Please Please Please! A picture of this event is posted below.


mcrowell75, I did not line up the butterflies with the hole in your album, I simply lined them up equally. I can use the idle thumb screw to increase the idle to the hole you note in your album. I like your method better and will use it next time the carbs are off the bike. There is a picture of the pickup in the thread "80-82 pickup coil cover removal". It does rotate but there is no cam lobe. The air cleaners are fine. 2011-12-07_15-04-46_560.jpg
 
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Was it really 2 quarts? Thats all the oil that SHOULD be in the bike. Not normal.

Like hough said in the other thread, a fair amount is normal especially if the bike is on the side stand.

Did the oil that came out smell like gasoline?
 
Yes, it was really about 2 quarts and yes, it did smell like gasoline. I can safely assume that the PO or PPO or PPPO overflowed the float bowls and the gas ran into the crankcase. I'm glad I've only run it for a few minutes since rebuilding the carbs. Looks like the petcock needs a rebuild also. Time to change the oil and get the timing dialed in.
 
Finally .... drained about 3+ qts total of gas/oil mix from the crankcase and filled with new oil to full mark on the dipstick. Hooked up my strobe light and checked out the where I was after setting timing by "guestimate" a day or 2 ago. I was just a few degrees off so I loosened the pickup sensor and rotated it a few degrees clockwise until I was exactly on the "LF" mark at 1200 RPM. The engine is really running smooth and strong now. All I need to do is put the tank and seat back on and give it a quick go around the neighborhood before starting the teardown and cafe build.

Many thanks to all who helped. It would have been much slower without your guidance.
 
One sure way to ensure that overflow won't occur is to fit a cutoff valve in the gas line,and use it to make sure there is no flow when not running. lha
 
Agreed. However, I'm planning to rebuild the petcock so it works as designed, even though the design is somewhat prone to failure. I'd really rather not butcher things together. I have installed an in-line filter gas even during testing, a lesson learned after rebuilding the carbs on my XJ700 and almost immediately plugging them up again.
 
I just removed the original petcock and fitted a plate and manual petcock designed for this purpose- no butchery needed. However, i certainly understand, and agree with, the desire to keep things as original as possible. For me, it's not about some vague idea of collector value (let's face it....) it's the fact that Yamaha designed things pretty well and when things are returned to the way they designed them, everything works very well. In fact, I believe this so much, I pretty much made it my signature.

idlescrewleft.jpg
 
HoughMade, that generally describes my feelings also. I believe the collector value of these bikes is close to $0 hence my intentions to do my first cafe build on this bike. However, mine at least is 30 years old and prone to failures from lack of maintenance from the POs. When maintained correctly, they are pretty durable machines.
 
Take the air filters off and while idling and opening the throttle, spray some starting fluid or WD-40 in there. If it revs up beyond what it did before, I'm afraid your carbs aren't as clean as you think or there is otherwise some sort of fuel restriction. If that still doesn't cause it to rev, check the timing and the only way to do that is with a strobe light on electronic ignition models.

Do your carbs have plugs over the idle mixture screws? If so, time to remove them and adjust the screws to 3 turns out (from a very, very light seat). The first 15% of throttle is almost all the idle mixture circuit and it contributes up to about 35%. If that is not all clear and working correctly, you'll never get past 2000 or so rpm to get the main jet on line.

from trial and much error, I have discovered that getting this circuit completely clean is difficult. I had my carbs apart and together at least 5 times before I got it clean enough to work right. Here is what I finally discovered to clean and verify that the circuit is clean:

1. With the carb off and the idle mixture screw in 3 to 3.5 turns and the enrichener (choke) in, use aerosol carb cleaner (I like Berrymans...and it will burn on your skin and melt any plastic in the area) and with the straw on, spray cleaner through the air jet at the carb inlet. While doing this look through the engine side of the carb. You should be able to see s strong stream coming out where the idle mixture needle is. If you don't, keep spraying until you do.

2. Once that is clear, turn the screw in and seat it lightly. Now spray the carb cleaner in the air jet again. It should not come out the needle hole anymore, but there are 3 tiny holes right above the throttle butterfly. You should see 3 distinct streams coming out the holes. Not trickle, not dripping- thre strong distinct streams. You may have to hold the butterfly open a bit to get a good view. If you can't, spray until you do.

3. With that done, turn the carb over and if the float bowl is not off, remove it now. Remove the plug on the idle jet tube. It is a smaller tube built into the side of the main jet. Then, with a small flat screwdriver, remove the idle jet. Make sure it is clean. the hole through it as well as the holes on the side should be clean. Use carb cleaner if you have to, but do not stick anything harder than the brass it is made of in any of the holes.

4. With the idle jet out, repeat the same procedure that you did spraying through the air jet, but this time spraying up from the bottom where you just took the idle jet out. With the screw in at 3 to 3.5 turns, you should see the strong stream coming out from the hole at the idle screw. With the screw lightly seated, again, you should see the 3 strong streams from the holes above the butterfly.

5. Re-install the idle jet and plug. Set the idle screws to 3 to 3.5 turns- reassemble everything else.

- if you do all this and actually see the streams of carb cleaner each time you should from each location, your idle circuit is guaranteed to be clean. If you do not actually see the streams where they should be when they should be, you can not be sure.

Finally, as to the main jet, you can look through it with the slide out and see if it is clean, but unless you take the emulsion tube out, you will not know if the holes in the emulsion tube sides are clean. With a broad screwdriver, take the main jet our, the firmly, with a flat punch or something wide enough to span the center hole, push the emulsion tube up from the bottom into the carb throat- remove, inspect and clean if necessary. Heres the kicker- I boiled my carbs in vinegar water for about 2 hours- twice, but when I finally got around to taking the emulsion tubes out, the outside, the part you cannot see when they are installed, were caked with varnish.

Good luck!
When you say the cleaner will melt plastic, did you pull the diaphrams and all o-rings out before cleaning? The choke has rubber too. I'm a bit confused.
 
It won't melt all plastic,as the spray tube that is used is made of plastic,however I wouldn't chance it. The diaphragms are made of rubber,but again,I wouldn't take a chance on that either. Probably best to remove any non-metal parts. lha
 
Take the air filters off and while idling and opening the throttle, spray some starting fluid or WD-40 in there. If it revs up beyond what it did before, I'm afraid your carbs aren't as clean as you think or there is otherwise some sort of fuel restriction. If that still doesn't cause it to rev, check the timing and the only way to do that is with a strobe light on electronic ignition models.

Do your carbs have plugs over the idle mixture screws? If so, time to remove them and adjust the screws to 3 turns out (from a very, very light seat). The first 15% of throttle is almost all the idle mixture circuit and it contributes up to about 35%. If that is not all clear and working correctly, you'll never get past 2000 or so rpm to get the main jet on line.

from trial and much error, I have discovered that getting this circuit completely clean is difficult. I had my carbs apart and together at least 5 times before I got it clean enough to work right. Here is what I finally discovered to clean and verify that the circuit is clean:

1. With the carb off and the idle mixture screw in 3 to 3.5 turns and the enrichener (choke) in, use aerosol carb cleaner (I like Berrymans...and it will burn on your skin and melt any plastic in the area) and with the straw on, spray cleaner through the air jet at the carb inlet. While doing this look through the engine side of the carb. You should be able to see s strong stream coming out where the idle mixture needle is. If you don't, keep spraying until you do.

2. Once that is clear, turn the screw in and seat it lightly. Now spray the carb cleaner in the air jet again. It should not come out the needle hole anymore, but there are 3 tiny holes right above the throttle butterfly. You should see 3 distinct streams coming out the holes. Not trickle, not dripping- thre strong distinct streams. You may have to hold the butterfly open a bit to get a good view. If you can't, spray until you do.

3. With that done, turn the carb over and if the float bowl is not off, remove it now. Remove the plug on the idle jet tube. It is a smaller tube built into the side of the main jet. Then, with a small flat screwdriver, remove the idle jet. Make sure it is clean. the hole through it as well as the holes on the side should be clean. Use carb cleaner if you have to, but do not stick anything harder than the brass it is made of in any of the holes.

4. With the idle jet out, repeat the same procedure that you did spraying through the air jet, but this time spraying up from the bottom where you just took the idle jet out. With the screw in at 3 to 3.5 turns, you should see the strong stream coming out from the hole at the idle screw. With the screw lightly seated, again, you should see the 3 strong streams from the holes above the butterfly.

5. Re-install the idle jet and plug. Set the idle screws to 3 to 3.5 turns- reassemble everything else.

- if you do all this and actually see the streams of carb cleaner each time you should from each location, your idle circuit is guaranteed to be clean. If you do not actually see the streams where they should be when they should be, you can not be sure.

Finally, as to the main jet, you can look through it with the slide out and see if it is clean, but unless you take the emulsion tube out, you will not know if the holes in the emulsion tube sides are clean. With a broad screwdriver, take the main jet our, the firmly, with a flat punch or something wide enough to span the center hole, push the emulsion tube up from the bottom into the carb throat- remove, inspect and clean if necessary. Heres the kicker- I boiled my carbs in vinegar water for about 2 hours- twice, but when I finally got around to taking the emulsion tubes out, the outside, the part you cannot see when they are installed, were caked with varnish.

Good luck!
I would just like to say that Houghmade you saved my life! OK maybe not that big of a deal but it has to do with carbs so we all know how big of a deal it actually is. I used your 5 step cleanning program and it worked great. Check out my pics your write up made its debut. Thanks again!!!!!!
 

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