XJ500 "Cafe" Build story :)

if you don't make mistakes you never learn.
we all learn from others mistakes

 

Quick update on the bike, I know it's been a while. Had the bike running well, at least I thought anyway. Had the guy do the entire technical check, import process, and registration. The day I got my plates, I drove it a couple miles to the school I work at, and the bike ran out of gas right as I pulled in our parking lot. It ran well right up until it ran out of gas. Started up fine no problems as well. It did sound low on gas, but I thought it was just warming up still. I got too excited and forgot to check the level before I left haha. Good thing it died at the school though. Well.... then I put more gas in it. It started up but was only firing on 2 cylinders? Pulled the plugs. 1 and 2 were pretty wet, scrubbed them, let them dry, started it up again and it ran, but sounded awful. After a little while the starter just stopped working... I've taken it apart twice and cleaned it up. The brushes are pretty worn down, so one or two of them aren't touching Sadly getting a repair kit here in Slovakia isn't as easy as in the US.

Meanwhile I took the carbs off and decided to check levels. #2 was overflowing some... So I replaced the pin and stuff in it. Checked levels again and they were good. Put it back on the bike and tried to push start it several times. And nothing.... So I'm at a bit of a loss.

So here is what I'm going to do, and if you guys have any suggestions let me know! As soon as I get the starter kit I'll replace those things. I'll first check for spark. Also pull the carbs off again, use an air hose to blow anything out, that maybe I missed. Check levels again. Do an oil change, because I haven't since I got the bike.

Could it be that running it out of fuel really messed something up? Or maybe from overflow of a carb there is fuel in the crank case? Would that cause the bike to not even push start at all? Open to any thoughts or suggestions of course.

 

when you refill the mikuni carbs you have to rap on the bowls to keep the floats from sticking and overflowing the carbs

 

Hoping the starter kit comes in this week. Geez it’s taking 3 weeks to get it here in Europe. Nonsense . Anyway, something I wanted to run by you guys. Sometimes when I turn the fuel to prime I watch it flow and then stop, as it should, because the floats shut it off right? then I put it on run. After the bike sits like a day I’ll go back and if I flip the lever to prime fuel will flow again like it’s filling the carbs? If the floats stopped the first time and fuel didn’t keep flowing, why after like a day would it flow again like it’s filling a carb or something? And then it will also stop flowing like it shut off. Thoughts?

 

fuel evaporates through air compensator jet in back of carb across from air jet. compensator jet passage goes directly into float bowl.
this is normal in the 550.

or your needle valves are not sealing properly has your oil level risen?

 

My bikes do the same thing. Since I'm not gaining fluid in the crankcases, I chalk it up to evaporation.

 

Update for anyone interested!

Firstly.... I ordered a starter rebuild kit from a guy here in Slovakia. He said the place said it would take a while. I said "well if it's more than two weeks I can have someone from the US bring it." because I know people that come over every summer, his reply "no! I already ordered it." 5 weeks later he says the contacted him and they can't get it anywhere... So I order from amazon in the U.S. have my brother send it to me. I get it in about 2 weeks. so 7 weeks later I get to fix the starter to check for the real problem why it won't start.

Replaced the starter parts today. Threw the starter on, boom! Turns over no problem. Wouldn't start though. Sprayed some starter spray in the filters, nothing. Pull the plugs and check for spark. 1, meh, 2 ok, 4 nothing, 3 not great. Plugs are new, and I thought maybe it was the wires, but I decided to check the coils. Of course I'm new to this so had to look up some videos haha. Both coils on the primary side (thats the plug into the electrical system right?) were about 3.9 Ohm. Checked the ends of the wires, with spark plug caps on. One coil was like 18k, the other one, nothing. So I'm guessing that one will need to be replaced.

Could it be that since I've fixed some things that it was too much and ruined the coil? I mean it's got quite a bit of miles on it and quite a bit of wear. Anyways, theres the update. Trying to find a place to order a new coil, and then we'll go from there. Also should I just replace both? or is just replacing the one ok?

 

might be easier to find 750 honda coils
@Jetfixer can tell you more

 

Interesting. I wonder which year. And why the 750? Do the coils basically fit the same? I found some for the xj550 but there about $120 each.

 

You can buy CB750 coils new from Cycle Recycle part 2 they are around 39.00 ea and they sell the plug wires and caps as well these fit into stock location you only have to flip them over .

 

Good to know! Which model or year 750? I have a place over here in europe I can order them from for about the same price. Just want to make sure it's the same thing as what you are talking about.

 

these are the two different coils I'm coming across for cb750's they have a crazy amount of models but all have one of these two it looks like. the site is wemoto.com

 

electrically the honda coils are the same as yours, you want the mounting holes to be the same, horizontal / vertical

 

Cycle Recycle part 2 sells these a kit these fit yamaha,honda,Kawasaki, but 80 to 83 are the ones to obtain , these have replaceable plug wires I have ran them for 3 years now runs great. If your in Europe realize shipping might be pricey . If your in the UK sure there are breakers that would have the coils.

 

Ok guys, so today I got the Honda cb 750 coils in. The ones with replaceable cables. So I clipped the original connectors off the old coils to connect to the new ones. The the new ones had + and - posts. So I checked the voltage from the connector on the harness to make sure I got the positive and negative correct. Hooked them up. The ignition coil I had on the right side sparked just fine. The one on the left one would spark really strong, and the other not at all. So I took the one that had both sparking and hooked it up to the same connector that only had the one to see if it was something with the connection. Both still sparked. So I went and checked the resistances like I've seen in a few videos and read about. I've attached the pics.

On 200 ohms the connectors on both read 2.5
On 200k ohms putting both tester ends into the two spark plug caps, both coils read 24.6

I even swapped the cable out with the one side of the coil that wasn't sparking and still nothing. So I don't think it's the cable. It's not the cap, because I swapped that too. No matter what I did that one side of the coil just wouldn't spark.

Things to note. That coil also was warm to the touch after the first time trying to check for spark. The one that had both sparking was not. Also the one that only had one cable sparking was an extremely strong spark and after I would depress the start button after a few seconds it would let off a spark. I got shocked a couple times.

Again this is all new stuff to me, so I'm trying to figure out some on my own, but legit have no clue about this kind of stuff. Is the coil just a bad one? Did I fry it somehow? Wouldn't the resistances be different if something was wrong internally with the coil?

 

https://www.hondatwins.net/forums/a...w-coil-works-dual-fire-ignition-coil_fig1.jpg
swap the sparkplugs, it could be a bad plug.
they can measure good with a meter but n0t work because a meter uses a little battery and when it's on the bike there's thousands of volts.
if there's not enough insulation someplace inside the coil, the high voltage will jump it but the meter battery can't so it looks good to the meter.
measure from the + and - to the mounting bars on the coil, should not be any connection

 

So good news. They sent me a new coil just the other day. Put it on today, checked all the plugs and they all spark. So I put the tank back on and flipped the lever to prime, waited for fuel to stop flowing and then tried to fire it up. Nothing. Which I expected so then I used some starter spray, it got a few pops out of the exhaust, but also a few other pops that sounded more towards the engine. Also... occasionally when I would let off the starter button, I think I heard a small spark somewhere? Could that be a short somewhere? I took the voltmeter and put the negative on the battery negative and then was touching random spots on the bike. Some parts of the frame would give a .01 reading. Also the positive cable to the battery was super warm for some reason.

So a couple questions. I'm guessing everywhere on the bike should read 0 on the voltmeter correct? Also any reasons why the positive cable would be warm?

and super important, and probably stupid question. Do the spark plug cables need to be put on a certain order on the cylinders? I know sitting on the bike from left to right it's 1-4. From the parts list pictures it looks like the left coil should go to 1 and 4 and the right coil should go to 2 and 3. But even with that are out of those two for each do they need to be specific? like looking at the coil which goes on 1 and which goes on 4? and same with the second coil.

Thanks again for all the help so far!

 

The ignitionis a wasted-spark system. 1 and 4 are a pair and fire both plugs at the same time, twice per revolution. 2 and 3 are a pair and fire both plugs at the same time, twice per revolution.

 

0.01 = 10mV = negligible.

 

Thanks for the help guys! Went back out and realized I had them switched up. Got them on the correct plugs and coils and with some spray started up and ran. Sadly had to keep the choke pretty open or it would die off, so it seems I'll need to pull the carbs off again and check them for different things and check levels again. It has sat for 2 months while I was waiting on parts so who knows.

 

The pilot circuit is easily blocked on these carbs - you need to get cleaner squirting you in the eye from the holes in the 'roof' of the venturi.

 

Update! So I cleaned the carbs, got everything back on, checked levels and things also. All were in tolerance. Bike fired up, even sounded good. Took it out for about 2 miles and seemed good. Then took it for a little longer maybe 5 miles. Let it sit for a couple hours, and started up again just to move it and it seemed good. Let it sit a couple more ours, then went to start it up to drive home, and it sounded really rough. With the choke open it wouldn't really do anything until it sat for a little bit, then it would rev up like the choke was open. I was able to drive it back home the 5ish miles, but it was a struggle.

So here are some things I noticed. If I have the petcock set to "run" it will work for about 30 seconds or so, then fuel will stop flowing.... I've replaced the diaphragm on it already, and also checked for leaks around the intake boots and found nothing. Also checked to make the vacuum hose isn't blocked. When I stop the bike, I usually put it to "run" just to make sure it isn't just flowing fuel into the engine freely, but seems like everytime I go back to it and flip it to "prime" some fuel flows into the carbs. I'm guessing I need to just set all the floats at -2mm just to be safe they don't over flow or something...

Also I put an inline fuel filter on the bike while doing this whole rebuild, because there was a crappy one on it when I bought it. Could it be the filter is causing problems with the vacuum? Like maybe it is pulling the diaphragm out enough but with the filter there its not strong enough? I don't know I'm just kinda shooting around.

The fact the bike ran awesome for a bit and then suddenly is running rough makes me think it has to be something with the carbs overflowing again and causing problems. Also... if they are overflowing into the crankcase... how big of a deal is it if some fuel is in the oil? Maybe thats a stupid question haha, but I might as well ask it instead of just assuming something. Thanks again guys. I should have recorded it when it was working well so you could hear it

 

Ok, just a small update. Went back out to the bike and it wouldn't start up. Pulled the plugs, some were a little wet looking... Pulled off the carbs to check levels... 1 is at like +2mm, and the rest are all like -4mm... Is there something that happens that causes the floats to change? I haven't messed with adjusting them since I got them all about -2mm and one was right at the lvl. So now they are off.. and I wouldn't be surprised if the +2mm decides to overflow sometimes...

IMPORTANT QUESTION. When I adjust floats, should I adjust one, then check them all? Or adjust them all and then check? Does the adjustment of one affect the other 3? Like if I adjust the one that is +2 to like 0, will it raise the others?

 

each carb works independantly from the other with the fuel level. are you saying your fuel level is even with carb/bowl joint (+2mm)
in this photo 3mm is spec
i do not know what the specs are for a 500
xj550
-Fuel level measured via the clear-tube gauge: 2mm +/- 1mm
thats 2 mm below carb/bowl joint.

make sure your carbs are level front to back and side to side. you can test this by using the tube and checking its "fuel level" to measure carb1 and 4 from same carb
just like a carpenters water level. also check front and back of carb.



Setting the fuel levels

 

plugs being wet after trying to start and failing to start is normal. I would look at ignition system and do a voltage drop test on battery when cranking starter.
no less that 10 volts when cranking.
my 550s are very fussy about the battery voltage when starting cold

it is easier for me to set level of fuel on 1 carb at a time get it in spec and then set the next carb.

 

Ok thanks so much for this info! I have been using my iPhone lvl to make sure carbs are level all around before checking the few levels. I always thought +2 meant 2mm above where the carb bowl meets the body. So really they should all be 2 below where the bowl meets the body?

Mine are all like 4 below and then one is 1-2mm above that line. I guess I was just confused about what the +and - meant when measuring. I'll mess with them some more in a couple days. Thanks again!

 

2mm below the join line +/- 1mm. This means that the fuel level can be anywhere between 1mm below the join and 3mm below for it to be in spec.

Setting the fuel levels

 

Hey guys... so I guess I only write when something goes wrong... That's too bad.

So I did everything we've been talking about. Carbs were leveled correctly. Replaced the coil that I thought was just a bad coil. Everything worked awesome. Sounded great. Started up. Took it out for a few short drives 20 and 30 minutes. Ran wonderful. I even took a video to show you guys how it sounds, just never posted it.

The bad news... as I was driving home, and I was about a half mile away, the engine sound changed completely, and I had to give it a lot of gas or it would just die immediately. So when I got to the garage I hopped off just to look, and one of my pod filters had fallen off (because I never tightened it I realized). So, I thought perhaps it was something with that carb. I pulled them off today cleaned it out, but it didn't have anything noticeable anyway. Put them back on. Started up with spray but sounded the same as before. I checked for spark, and both inner spark plugs weren't sparking. I immediately felt the coil powering those two, since I had a problem before, and it was warm... Did the same tests as before, swapping spark plugs, switching connectors, etc... no spark. So something went wrong with the coil. No idea how or why.

What are your thoughts? It ran several days no problem, and then in the middle of a drive it just stops working? Everyone said the cb750 coils work with it, and the seemed to be. Maybe where I have the positive and negative wires that hook into the harness somehow touched the frame? I tried to wrap them in electrical tape so they wouldn't touch the frame. I'd hate to have to buy 2 more yamaha coils since they are about $110 a piece, but if it's an issue having the cb750 I don't want to keep putting out for them either...

 

Also... it seems both of those spark plug openings are stripped on the frame now? No idea why. One I knew happened before I got the bike running well, so I would just tighten it with my hand until it was tight and it ran with that. But today when I checked the other one it also just kept turning. Perhaps that is why something happened with the coil?

Has anyone ever rethreaded a spark plug socket on their bike? I've seen videos about kits and that it's possible. Just not sure.

 

To re-thread the spark plugs holes you have to pull the head off, so you might as well just replace it. if the coils are under warranty send them back. Check the connectors from the TCI to the coils and make sure they didn't come loose. If you didn't already try swapping the connectors from the TCI to coils to make sure its a bad coil vs bad TCI.

 

Not sure if I can find an XJ500 head around. Although I did a search just now and found something for an '89 XJ500 Maxim? Anyone ever heard of that? It's in Romania, not far from me actually.
https://bnb4moto.com/en/moto-parts-oem/930-cylinder-head.html

I did try swapping the connectors, I know for sure it's the coil. However, it could be my error, as this is the second time I don't think they'll replace it for free again. Especially if they found out I'm putting it on an xj and not a cb.

 

I dont know if it does. There are others that will know if it will fit your motor.

 

Why a coil might go bad:

On the secondary side there is an open in the plug wire or cap that creates a larger air gap than the internal insulation within the coil and the high voltage finds a path to ground through the internal coil insulation. The result is the coil enameled insulation is burned and eventually breaks down and consequently becomes a lower resistance path to ground even after the above is corrected. Did you replace the plug wires and caps with the new coils? Did you ohm the secondary to the metal bar as Polock suggested?

On the primary side the TCI is misbehaving. First, if an increase in dwell occurs the effective on time of the coil becomes excessive and damages the primary winding from overheating. I don't know for sure but I suspect this would show up on the meter. The earlier measurement you made was 2.5 ohms, which is right at spec, but typically they read just a bit higher. Compare that reading with the working coil. The second issue with a TCI that can occur is the safe mode for when the bike is not running and the key is on. This can easily be checked by measuring the voltage on the gray and orange wires when the key is set to run at either the coil or TCI. One of those two should power up low, and then approximately 2 to 3 seconds later it should switch to 12V. Whether it is the orange or gray wire powering up low is dependent upon the position of the reluctor, however whichever one does power up low should produce a spark on the applicable plugs when it switches to 12V.

When you said the coil was warm was it like hot to the touch and obviously warmer than the other?

Replacing the head or even pulling it to repair damaged spark plug threads seems extreme. You can find all sorts of examples on here where helicals are installed but taking precautions to ensure the swarf does not drop down into the combustion chamber.

I would never run an engine with a loose plug as depending on how bad it is air can be pulled into the combustion chamber causing it to run excessively lean.

 

I wouldnt take the risk of putting in a helical into the spark plug hole without pulling the head off. if the debri gets in between the rings it can damage the wall. Take it to a machine shop to do it to make sure it goes in straight and piece of mind.