Here's my story! Im so happy I could cry! Still need help

Here's my story.

I'm the second owner of this bike. I got the bike with 3500 miles on it. It never had any power but I thought it was b/c it was a 400 twin and always thought 60 mph was its top speed (took forever to get to that). I've had the bike for 15 years and always living in an apartment, I left it at my folks home and rode it a 100 miles a year. Finally bought a house with a garage. After talking to people on here, I decided to take the carbs apart and check them out for vacuum leaks. Sure enough found a diaphragm with pin holes in it. Replaced it and cleaned everything real good. Looked at the floats and never messed with any of that---just put new gaskets on the lower bowls. Replaced all rusty hardware, made sure all the little passages were clear and reinstalled. Never split the carbs and didn't mess with the sync. Never messed with the float levels. In the meantime, cleaned and sealed the gas tank with Redkote (which is now blue). The petcock was beyond repair so I replaced with a new one from Yamaha with new lines.

Finally got it all back together and it runs and runs hard!!!! Meaning I can hit 70mph in under a minute!!! I did a chop block and checked the plugs---looked real good and almost too clean. I tuned the mixture at idle (after being warm) by ear---remember I have twin with each cylinder having its own exhaust. I added an inline fuel filter between the petcock and carbs.

So here are my questions. When the bike sits. The fuel filter (clear plastic with paper element) fills up with fuel. When I ride, the fuel is drained out of the filter until the paper element starts to turn dry. But the bike then pulls enough fuel through the petcock to keep running. I checked the vacuum line and plenty vacuum there while bike is running. I pulled the fuel line and turned to prime---fuel does poor out. Also while riding, turned to prime and no change--the filter stays empty and almost dry and the bike only pulls what fuel is needed. Is this normal? Or do I need to check float level? I know my bike is only a 400 and uses minimal fuel (I think I get 55 mpg) but shouldn't the filter be full? Another issue is that between 6-9000 RPM, it seems to "miss a beat" or a real slight hesitation. In my mind its because of lack of fuel, or is it just because I have a small 400cc that is being maxed out on power?

I had a yama dealer check valve clearance years ago and have barely put miles on it since. I now have 5500 miles on the odometer. Do you think I need to do it again?

I'm just so happy that I can actually ride it. I took it out yesterday and put over a 100 miles on it both highway and in town. Its been such a headache trying to get to run right I almost sold it a couple of times. Thank you all for so much help here. I now want to get it to run top notch!

 

Re: Here's my story! Im so happy I could cry!

My 400 does the same thing from 6-10k, I'm thinkin it's a fuel starvation issue as well. Even on prime it does it, and i've checked my float levels just last weekend and they're fine.

I've wondering if somethings not quite right with my jet needle raising. I know my carbs are prestine, (not a clunk test issue) but it just seems to go from rich to extremely lean from 1k RPM to 10k.

If i check plugs when warm and idling for a min plugs are good, but if i do chops at 5k RPM they're white. I still haven't found a reason for this yet.

 

Re: Here's my story! Im so happy I could cry!

Prime doesn't always guarantee flow. If the petcock is in need of rebuilding, it can be bad in any position.

 

Re: Here's my story! Im so happy I could cry!

I took my petcock apart even though its new and it looked great.

 

Re: Here's my story! Im so happy I could cry!

my plugs look hot/lean as in these pictures. but I think they are ok.

pic #23 are what my plugs are like after a long ride at 5000 rpm

http://www.dansmc.com/Spark_Plugs/Spark ... talog.html

 

Re: Here's my story! Im so happy I could cry!

My petcock is new last year, and I know from an unfortunate experience that it flows good

I actually was thinking of shimming my needle, the clip adjustment puts it up too high, (bogs out when applying throttle at speed) so shimming may give me a happy medium setting.

I actually was testing something the other day, and noticed the air inlet under the seat, well it's throat closes on it's self a little (like 1/8") when i snort it from idle. So i guess i don't have any air leaks

 

Re: Here's my story! Im so happy I could cry! Still need h

A pic of the fuel filter full.

 

Your filter should stay full while running.
It's gravity fed, fuel runs until the needle vavle closes.
Very strange.
If you pull the fuel line at the carb put it in a container and start the bike. Does gas flow freely into the container?

 

Re: Here's my story! Im so happy I could cry! Still need h

Yes, it flows freely. The vacuum is good enough to open the petcock (which is new, but I still took it apart and found nothing wrong).

This is what made me think its float levels that need adjusting. Am I thinking wrong?

 

Re: Here's my story! Im so happy I could cry! Still need h

Here's the latest drama. The wife and I woke up at 3 am to because the house is filled with gasoline fumes. I guess there is gas coming through the carbs and out the back where the air filter is.

What the hell? Now what? Is that a stuck float?

 

check float levels and float needle valve seal. check bowl drain screws. check that bowls are screwed on properly and gaskets fitted correctly.

sounds like stuck float/bad seal on the valve

 

Last time I had it apart, I put new gaskets on the lower bowls. I have used the drain screws but they are tight and do not appear to be leaking. I'm thinking its inside the bowl with the float needle and floats???

 

Try tapping the side of the bowls with the handle of a screwdriver...
may loosen a stuck float.... otherwise you'll need to pull them again and give them a good cleaning......

These guys have a bit more power than people suspect....

 

Re: Here's my story! Im so happy I could cry! Still need h

If you get a puddle of gas when parked, your petcock is not working. Period. When the engine is off, the petcock should not allow fuel to pass (unless you left it on Prime). So your "new" petcock is either bad or maybe you got the diaphragm cockeyed when you reassembled it. Maybe your needles need to be fixed too, but the petcock for sure needs attention.

If your filter is running dry, then the petcock is not supplying fuel fast enough.Maybe there is something clogging the petcock internally or covering the intake screen that pokes up into the tank. Maybe some RedKote broke loose and is causing problems?

FYI I hate the stock Yamaha petcock. I junked mine and got a manual aftermarket one.

 

70 Miles per hour in under a Minute??? Holy Cow!

If it still starves-out ... try a cheap trick.

Wrap the Fuel Line with some "Spiral Cable Wrap"
Radio Shack.
Wrap the Fuel Line.
If the Fuel Line is "Kinking" and shutting you down ... wrapping the Line in Nylon Spiral Wrap will keep the Fuel Line (and Vacuum Line) from kinking.

 

haha, that 70 mph statement was in the old days before I found a diaphragm with pin holes in it. Once I replaced it, then the bike ran like a ......... (you get the point). Now I am fighting problems of old age. The bike has sat for many years (one season outside, my bad---young age on my behalf). Now I am trying to get things straight and learn at the same time.

The fuel line to the carb from the petcock is new and pretty stout. Same as the vacuum line that opens the petcock---all new. Seems pretty tough and I don't see it collapsing but I could be wrong. I checked the vacuum opening in the carb nipple and its clear. Started the bike and had good vacuum.

On this forum, I am asking for advice and getting mixed answers. Is it in the carbs? or is it in the petcock? Time to check things out again. Thanks everyone for pointers.

 

The leaking fuel when parked has to be a problem with the carbs, most likely floats. Even if on prime, if the floats are closing properly at the correct level, fuel will not leak.

For fuel to leak on anything other than prime, means that in addition to the carb/float issue, the petcock mechanism is not working properly. If the petcock is working and it is set to either ON or RESERVE, it is not supposed to flow without vacuum. That is an easy test: disconnect the fuel hose from the petcock and see if it leaks when on ON or RESERVE.

Finally, as the fuel should be flowing freely to the filter with the vacuum, for the filter to run dry means either the carbs are pulling far too much fuel, faster than the petcock is designed to provide it, *OR* when you are going faster than you are going when parkied, the petcock is not able to meet the normal, expected demand.

It could be that something is slowing the fuel flow into the petcock from the tank side so it can flow well enough when testing, but not well enough when your are going 60mph down the highway. Maybe they sold you the wrong petcock?

I know the problem of assembling carbs and not getting a diaphram set properly. Fortunately I noticed *before* I mounted the carbs ...

St. Francis of Asissi would have some choice explatives for the engineers who designed the install/removal of these carbs.

 

Leaking FUEL when Parked points to a faulty Petcock letting Fuel continue to flow after the Engine is stopped.
Without Vacuum supplied from a running engine the Petcock should be OFF.

Test the Petcock.
Run a hose from the Petcock Outlet to a Bucket
Run a Vacuum Line to the Vacuum pick-up on the Petcock.
Set the Petcock to:
PRI = Prime = Gas should flow out of Petcock.

Set Petcock to:
ON = Run = Fuel
Petcock should NOT be allowing ANY Fuel to flow into bucket. Off. None.

If the Petcock Leaks Fuel or lets Fuel dribble or drip out. Rebuild or Replace.

Test Vacuum Valve:

Place the Vacuum hose to your lips and draw the air from the Vacuum Line.
Petcock should allow Fuel to flow while under vacuum; stop when vacuum is released.

There are two Schools of though on Petcocks.
Rebuild.
Get a New One.

I used to rebuild them. But, I no longer have faith in the Parts supplied in the Kits.
Others will tell you to buy a Kit.
I tell you to buy a new Petcock.
The Old petcock lasted damn-near 30 years.

Same deal on the Carb Floats.
Close to 30 years ought to be good enough reason to replace the Floats.
The Kits for that I endorse and have installed for many a client.

 

Here is an update.

Changed oil and filter due to gas draining into case.

Cleaned the petcock and installed new o-ring. It was clean as a whistle and works great. I sucked on the vacuum line and also I turned to prime---both ways have good fuel flow. Left the line off and no bypass leakage.

Ordered new needle valve seats for the floats and installed. Reinstalled carbs onto bike and set float levels.

It runs but not as smooth as I would think. Rode around for a while, the fuel filter went dry again but the bike keeps running (pulls just enough fuel through it)

Came home and removed the gas cap and put some duct tape over the hole with a hole for ventilation. Rode some more and the fuel filter stayed half full. So I guess its in the cap. I removed the rubber gasket and most of the parts. Cleaned everything up but it still causes the filter to run dry. What am I missing?

If I order a new cap---can I change the locking mechanism over so I don't have 2 keys????? Anyone ever done that?

As for tuning on the engine--Is the only adjustment an idle mixture adjustment??? Am i missing any other adjustment? Any adjustment at higher RPM? Its rained the past few days so I am on hold for now.

Once again, thanks for all the help.

 

If you aren't getting Full Power ... You have to remove the Emulsion Tubes and Clean them.

 

Yes that should be possible. You may want to have a locksmith do it, because some types of lock cylinders spring apart and send bits flying when disassembled.

 

^And these ARE one of those types!!

 

So after walking away from it for a couple of days, I'm back in the saddle.

Earlier I was convinced it was my fuel tank cap not letting fuel go through my petcock which caused a dry fuel filter. I took the fuel cap off and put some duct tape over the hole with a vent and made a ride. The fuel filter filled up! But then I made a couple of more rides and it dried up. I am now on the search for a used Petcock!! I have a brand new one in right now from Yamaha---but it just doesn't make sense. If I take the line off from the carbs, I get NO fuel flow (or leakage) in the On position or reserve. I turn it to prime and fuel flows fast and great!! I reattach the line to the carbs with a clear fuel filter, and it will NOT fill the filter on ANY position(with the bike running at different RPMs). What the Heck??? I give up on this petcock!! I checked the vacuum line, I've disassembled the petcock multiple times and put in new o-rings with same results.

As for the bike. It runs great! I set the idle mixtures on both carbs to about 3 1/2 turns out from seated and by listening it sounds good. Rode for awhile and pulled the plugs which look nice and clean. At higher RPM's/speeds, It does have the slightest hesitation or the slightest miss but still has power. I take this do too the minimal fuel going to the carbs. I don't think I will mess with the carbs anymore until I get this petcock situation figured out.

Thanks once again for all the advice and help. Feel free to add comments.

 

The factory vacuum-operated petcocks require vacuum from the intake manifold (via the small rubber line connected to the petcock) to "open" the internal fuel valve when set to the ON or RES positions........that is the "automatic" part of these petcocks. No vacuum signal = no fuel flow in the ON or RES position. Engine on (or some other source of vacuum, like sucking on it for testing purposes........) = fuel flow in the ON or RES positions.


When set in the PR (prime) position, the petcock should flow fuel ALL the time, whether vacuum is present or not. This position is normally used only to fill up the carb bowls after the carbs have been removed from the engine for rebuilding, etc., or during a fuel level check.

 

Make sure that you have the Filter installed with the right FLOW pattern.
There's probably an arrow on the Filter.
Blow through the Filter. If there's a heavy resistance; change Filters.

"Air-Bound" Filter

If the Filter is positioned in such a way that the Fuel from the Petcock is battling an Air Bubble trying to escape the Filter and rise to the tank ... the Filter will prevent the Fuel from flowing.

To eliminate this problem ... situate the Filter with the Inlet and Outlet situated VERTICALLY.
Then, Let the Filter Fill-up. Prime it.
The Filter that is Full and empties ... has a vacuum space letting Fuel fill it.

A non-primed Filter has an Air Bubble wanting to escape.
Fuel entering the Filter battles the Bubble being compressed or trying to escape from the Filter toward the Petcock and Tank.

 

Thanks Rick, I bet this is my problem. my bike will run good on On but only for about 10 minutes, then I can't give it gas, I reach my hand down and turn it to Prime (after a rebuild and proving it works ok) wait a few seconds and vroooom. problem is, I'll pull back in the drivway after the duration of the ride and the site glass'll be full

Just checked and my filters perfrectly horizontal. thanks again. just got to fix that damn igintion keyswitch

 

Don't bother trying to FIX an Ignition Switch.

For time and labor its cheaper to get a NEW one.

 

Re: Here's my story! Im so happy I could cry! Still need h

My filter has an arrow on it and its going the right way.

Heres the crazy thing. I rode the bike and the filter was dry the whole time. I took the gas cap off and still the same. The harder I rode the more dryer the filter got. I could see it turn a lighter color. I park the bike and the filter stays dry for 24 hours. Then in 48 hours it somehow fills up. What the heck??

 

The last time I had the carbs apart, I replaced the needle valve assemblies with new and set the float height. The floats should stop the fuel flow to the carbs while the bike is sitting there, but after 2 days my filter has slowly filled up. (it looks like the pic earlier in this post). But then I go ride and it drains that filter, to the point the paper element looks dry, but the bike keeps going as it slowly gets just enough fuel to run. 99% of the filter and housing is dry!!

I swear this bike is evil.

 

Notice my filter is not horizontal or vertical---Is this OK????

 

Yes. Its almost full.
Once the Fuel starts flowing ... the Filter will drain-out to the Carbs.
That space is a partial vacuum.
The gas will pass through the Filter without delay.

 

Re: Here's my story! Im so happy I could cry! Still need h

so are you saying its normal that the filter goes from this look (almost full) to completely empty when i start riding?

Do you think I have a leak in the petcock because with a couple days of sitting, the filter fills back up? Before I changed the needle sets in the carbs, fuel would overfill the carbs and leak into the case. I seem to have that problem fixed now.

 

It depends on how efficiently your Petcock is working.
If the Fuel from you Tank doesn't Flow-out of the Petcock at the same rate the Fuel Filter will allow Gas to pass through it ... The Filter will become "Empty" as Gas trickles through it to the Carbs.

If you think that the Fuel from the Petcock to the Filter isn't flowing fast enough...
Use a short length of "Square" Weed-whacker Line ... and PROBE the Petcock Outlet for a possible Obstruction.

You have to have the Tank on the Bench.
The "Face and Switch" of the Petcock off and out ...
Probe the Outlet with the Nylon Line and look for:
Sealant, Rust chunks or Varnish build-up.

If you have anything "Gooey" use Nail Polish Remover to get rid of it.
(Rubber Syringe flush it)