My bike's engine won't rev up

Dear XJ 500 users and experts!

I'm a new member from Hungary, also a proud owner of a 82' XJ 500 since 2007.

This is my introduction, and my ask for your help.

She is my first bike, I bought it a few months before I got my driver licence. I bought her with 65.000 passed km in her tachometer, and in the last five years I added another 40.000 km to them without any troubles. I nursed her, like a baby, she got all the care I could give her. Except one breakdown, ( clutch gave up: loose nut made it stuck ) she never left me on the side of the road.

Last summer found us with heavy oil consumption, and oil strains all over her engine, as most of the sealings gave up at one time. The clutch also started to work slippery, and no oil change could stop this, making riding her very uncomfortable. I was lucky enough to have an other XJ500 from the same type, though this one misses some parts. I bought it in the price of scrap metal. The donor bikes engine was complete, and as we took it apart, we found out, that it looks like new from the inside. So it was time to make one perfect bike out of the two.

Restauration progress went on fine: main engine parts were replaced, such as the cylinders, camshafts, pistons, etc, and also the clutch. She got a new paintjob, seat renewed, and lots of her parts were polished. Sealings were ordered from Japan. I also replaced her black chrome Sebring 4-1-1 exhausts system for a Jama Engineering 4-2-2. In my opinion, this kind of bikes shall have two pipes...

I started to experience troubles only at the test ride. Under 2000 rpm, the engine won't rev up, when i try to start and accelerate. This won't happen in neutral gear, when I play with the throttle, only just a bit. Carburettors were checked several times, we got their parts replaced, polished, but the problem still exists! Besides, when she leaves 2000 rpm, she runs like a dream. Her exhaust gases smell like she got too much petrol in the mixture, but whatever we do, it will not help, including changing the mixture. Sometimes, petrol floods some of the cylinders, so they stop. The engine drowns in petrol.

Anybody having any ideas, how to solve this problem, please help here in the forum! I love this bike very much, and I have lots of energy (and money) invested in her. I could buy another bike, but no bike I have ridden got me so much, so there is no way selling her and look for another ride. I took her for several bike meetings in Hungary, and it made me very proud, that sometimes she got more attention from visitors and other bikers than a new model from some much more exclusive brand. And that was before the restauration!

Please help! Any help is welcome, and appreciated!

P.S.: I added some pictures to my gallery, if anyone is interrested. They represent her state before the restauration. New pictures will be added soon, as the progress finishes, and she will be up and running fine. Sorry for my bad english. I'm counting on You!

 

Welcome to the site !!

First, since English is a second language, or you are using a translator, that's no problem, but you will need to bear with our explanations.

Second - you have a bike that meets an "under 500CC" spec for your country, and the carbs may be different.
Can you post your VIN or Engine number for reference ??

Your carbs may be running rich due to worn needle/seats
Your "slider pistons" may be sticking and need cleaning
your Pilot - Idle system may be plugged up.

quote -
but whatever we do, it will not help, including changing the mixture

Can you tell us what you are doing with this statement ??
You need to re-set your carbs to the correct specs, with some new parts, available here, shipped worldwide.

 

When you rebuilt the engine... what did you do to the carbs?

 

Thank you for the quick answers!

The engine number is: 5N4000306, same as the case number.
The pistons were cleaned at least two times, they were checked, they don't stuck. The needle valves will be replaced as soon, as I get the new ones.
In my country, there are no 'under 500ccm' regulations. There are 125ccm, 250ccm and 'above' categories, when you get your driver licence. And this doesn't mean any modification to the bikes, they are stock, unless user modifies them. My bike came from neighbouring country, Austria, I don't know their regulations.

When we reassembled the engine, we did nothing to the carbs, because there was no problems with them before. After the first test ride, when the problem occured, we took the carbs apart, and cleaned them, but it was no use. We tried to lower the fuel level inside the carbs, but that didn't help either. We also changed the fuel/air ratio, in case it was too rich in fuel, (in Hungary it's called "mixture") with no better results.

 

Carb threads -

http://xjbikes.com/Forums/viewtopic/t=2 ... yards.html
http://www.xjbikes.com/Forums/viewtopic/t=14692.html
Some pictures and detailed instructions here, but they are not your carbs
http://cycles.evanfell.com/2008/09/how- ... right-way/


Are you setting the floats with Petrol and a clear tube??
http://xjbikes.com/Forums/viewtopic/t=2 ... carbs.html

Did you syncronize the carbs with the YICS passage blocked ??

While the motor is warm, try adjusting the Pilot screws in (clockwise) until the cylinder stops firing, then out 1/4 turn. Should be around 2 turns out from bottom.

 

We did everything as mentioned, we tried the screws overnight. Nothing.
What is the YICS passage, You mentioned?

 

First, can we clarify if you have a 528CC or 492CC motor??

General information
Model: Yamaha XJ 550 H
Year: 1981
Category: Classic
Displacement: 528.00 cc (32.22 cubic inches)
Engine type: In-line four
Stroke: 4
Power: 50.00 HP (36.5 kW)) @ 9000 RPM
Compression: 9.5:1
Bore x stroke:57.0 x 51.8 mm (2.2 x 2.0 inches)
Fuel system: Carburettor
Valves per cylinder: 2
Fuel control: DOHC
Starter: Electric
Cooling system: Air
Gearbox: 6-speed
Transmission type final drive: Chain
Front brakes: Single disc
Rear brakes: Expanding brake (drum brake)
Speed and acceleration
Top speed: 176.1 km/h (109.4 mph) [what??]
Fuel capacity: 14.98 litres (3.96 gallons)

You have dual front discs and an oil cooler - and a strange seat, and spiral rims.

Do you have 2 - 12MM bolts in the block, below and in front of the carbs??
This passage inter-connects the intake tracts of the 4 carbs, and should be plugged with a special tool in order to properly tune the bike.

 

The motor is 492ccm type, and everything else you wrote, is correct.

 

Remove the 2 - 12MM bolts, and stuff the passageway with oil soaked cotton rags, then sync and tune.

Search YICS on this site.

Other worthwhile items - -

Valve lash adjustment - check.

Condition of float needle - seat, and verify float levels with gasoline.

Alternator brushes and fuse box. (in case you get bored with carbs :wink: )

 

Thank you!
I'll let you know, if it worked.

 

All the float needles are replaced, and the engine runs fine.
Problem is, that only while it's cold.
When the engine warms up, it stops, and it can't be restarted until it cools down a bit. The symptoms are the same as mentioned above. The engine seems to get too much gasoline, and it stops. What can we do now?

 

Pull the Plugs.
Determine if the problem is RICH or LEAN.

Following a Carb Cleaning it might be misplaced AIR Jets.

If it just dies; its likely Starvation.
One of the first things to check is: Gas in Tank???

 

+1
In addition, flow-check the petcock (fuel tap)
This checks it's flow AND the tank cap vent at the same time.

Anything can go wrong on a 30 year old bike.

 

There is gas in the tank , and the fuel tap is connected to the carbs via transparent tubes, so I can see the fuel flowing through. It should be O.K. I'll check the air jets next time.

 

This step is very important and can cause the symptoms you're describing.

Here is a "how-to" article; there is a chart with the specs included. You have Mikunis BS28's. http://www.xj4ever.com/setting%20fuel%20levels.pdf

 

Air jets OK. Going to check float level again.

 

Everything checked, seems to be O.K. But the engine won't even start now.

 

These bikes like a fully charged battery - the coils won't fire if you are below 90%

Bump- start the bike if you have to, let's get you running again.

 

No use, whatever I do... No start, sometimes the exhaust pipes take a loud "shot".
Is it possible, that the ignitor box under the seat has some trouble? When i bought the bike, it was wrong, i had to have it replaced, cause only two of four cylinders was working. It sounded like now, but with at least two working cylinders...

 

Timing? Did you change the main and pilot jets out after going from 4-1 to a 4-2 exhaust?