XJ650 Starting issues

It currently idles fine, and the technician from October said that they had synced the carbs and rebuilt them, but one and four, the compression seems to be low, and I don't know the last time a valve adjustment has been done. So I'm leaning towards. I need to do a valve adjustment into clean the carbs and resync them. I just don't want to, it's so involved. I was debating paying somebody else to do it, since the tech that I'm thinking of bringing it to next month, says there should be a leak down test, but I also don't want to do that either. I'm just frustrated.

 

All right, so I bought the valve clearance kit and the deluxe carb tuning kit, and I also bought the carb tuner pro, but I don't yet have the ability to pull and clean the carbs.

But I was going to check the valve clearances so then I could order the appropriate shims later.

Since I have the tank off I figured I would pull the ignition coils and check their resistances. Both of them have cracked housing

Coil 1&4
Fluxuates but it hovers around 3.0 ohms on the molex connector side
This is steadier, and is around 12,080 on the plug side

Coil 2&3
Also fluxuates but also hovers around 3.0 ohms on the molex connector side
This one doesn't read, just says overload?

 

Why is there red gasket gunk on everything??

 

Because when you can't find the leak you put red gasket gunk everywhere and cross your fingers.
I use black RTV personally.

 

0.L might be open circuit.
If the bike is firing on all 4 then that may be a dodgie reading though.
Copper is an issue with the plug leads and shortening them to give clean copper a chance works but obviously makes the leads shorter.
The screw in plug caps rely on a good connection but with water ingress can cause the inner copper to corrode away. Problem within a problem.
The cracked coils I think are generally not a huge issue and can be repaired with some general effectiveness.
In saying all of that. Dynatek coil replacements and leads(carbon core crimped) take that out of the chain. So to speak.

 

I think I'm going to replace the coils, they're firing but seem slightly out of spec on the ignition side.

Incidentally, 2&3 are the ones that aren't giving me any issues, best I can tell.

Also the fork is still leaking so I may just suck it up and see if chacal has a single fork tube for this thing

 

You're supposed to measure with the feeler gauge when it looks like this, right?

 

I haven't pulled the shims yet, but this was the feeler gauge that I could see.

The measurement I wrote down was the size that fit through the bottom of the camshaft and the top of the valve shim. I pretty much started at the listed size and then moved down until one of them fit.

If I'm understanding this right all but one of the exhaust valves is out of spec?

 

I'm not sure what I'm doing wrong, but I think the tools installed correctly but I can't actually get at the shim

The metal rim is not going down for me to grab at it

 

I am not sure what happened, it didn't look like the tool was working, but the top of the camshaft was pointed 180° away from the tool, And I was going to move the tool cuz it didn't seem like it was doing anything, I go to unscrew the little bolt that holds the tool on, And I hear a large pop.

I swear of course thinking that maybe I broke something but I have inspected everything and I don't see any cracks anywhere, and the tool is undamaged. I'm thinking maybe releasing the pressure on the screw caused the shim to move up, and maybe some oil that's on top of the shim was what I think came up as a result of the movement?

I'm not sure what I'm doing wrong and is the guide that I'm reading on the forum isn't quite clear enough

I can't get the shim out of the bucket because the shim is moving with the bucket

 

It sounds like you should be able to push down on the notch with a screwdriver and then get the shim out of the bucket, but not a single one of these seems to work in that way, there's an air compressor nearby and I was hearing you could blow some compressed air to try to get the shim out of the bucket slightly, but I think I might have to put this aside for another day.

 

That tool works, but it's a pain in the ass and if you get it wrong it can bust a chunk of your head casting right off.
Personally, I always use the zip-tie method (search on here or just google it).
Secondly, get a set of surgical forceps to allow you to get a grip on the shims.

 

Last shim check i was replacing a head. Couldn't get that tool to work properly. Ended up just removing the cams between checks. Yes painful. I will try the ziptie method next time.

 

I kind of wish that you could just detach the chain and the camshaft and then just put stuff back, because that would be way easier.

And based on one of those photos, it looks like maybe the chain had already gotten replaced at some point, because there is different colored link on the chain. But maybe that's normal?

I gently touched the chain and gently pulled it a little bit, it seems pretty tight.

 

The shim is Hydraulically attached with oil. Imagine separating two pieces of glass with water between. I use a small sharp screwdriver to pop it apart.

 

I plan on going back Sunday, and then trying again. Maybe it'll be a little bit easier.

From that sheet I posted, does it seem like seven out of the eight shims probably need to be replaced? Some of the tolerances on the intake shims are extremely small.

If I have to replace seven shims that's like 80 plus bucks

 

Most cam chains are replaced with a link. Otherwise you are looking at removing the crank and looping over. Unless you are splitting the engine you don't want to go that far.

 

Don't forget that clearance means the valve is closed. Too much and it opens too late. Too little and it is always open. 0.05mm is a big jump between shims. If you are in the ballpark spec then you are good.

 

I've always found one of those small magnets on the end of a stick very helpful when removing shims. +1 for the zip tie method as well. A piece of stiff home electrical wire will work as well.

$3.99 @ Harbor Freight...

 

Valve Clearance Intake: 0.11 - 0.15mm (= 0.0043” - 0.0059")
Valve Clearance Exhaust: 0.16 - 0.20mm (= 0.0063” - 0.0079")

Intake (from left to right)
0.03mm, 0.1mm, 0.08mm, 0.03mm
Exhaust (from left to right)
0.15mm, 0.2mm, 0.15mm, 0.13mm

If I'm understanding this correctly, one of those exhaust shims is basically perfect on the upper end of things, and two are 0.01mm out of spec tolerance. The last is substantially more.
For the intake, cylinder 2 valve is 0.01mm out of spec, the rest are substantially more

Also, why are the intake shims so much tighter than the exhaust ones?

 

Well that is a mess. Do your calculations removing 0.05mm for the right shims. You will notice that the spec is within 0.04mm which means on the mark will make a shim change just as bad the other way. You want minimum clearance and not more than maximum clearance. Obviously extracting the actual shims and seeing what you have is essential before anything changes also. I think there may be a shim bank in the American area also....

 

Yeah, now that I look at it, because you have to do some math for this, it looks like I'll probably have to go down two shim sizes on two of the shims? Oof

This bike only has 12,500 miles

 

Freaky. To be sure. You'd think it would be very odd to eat into the valve seat that much on low mileage. Check again to be certain.

 

I'll check again on Sunday, but, I'm pretty certain. I started at the highest tolerance level, from the feeler gauge that I got from chacal, and I worked my way down. I made sure that the top of the "egg" of the camshaft was as close to 180° away from the shim as I could, but it's certainly possible that when I measured it it was 185° or 175° or what have you.

 

The head I just replaced had no tolerance at all. had to find smaller shims just so I could check the actual tolerance. It is what it is. Have a search you might find someone swapping shims. God knows I have a multitude but am across the pond.

 

In thinking about this also, I think this also explains why the compression test that I did, that cylinders one and four are substantially lower than two and three. The clearances on two and three are not bad, all things considered, but two of the shims on one and four are two sizes out of spec, terrible lol

 

Shim source with good prices....... https://www.mikesxs.net/valveshim-25mm-230mm-310mm-honda-yamaha-triumph-g.html

 

I was able to pull the shims!

Exhaust (L->R)
2.7 2.65 2.7 2.75
Intake (L->R)
2.95 2.95 2.95 3.05

Apparently, someone had set cylinder 2 exhaust shim not upside down, because it was unmarked.

So yes, I need to buy 7 shims, and two I need to go down two sizes. I measured each one with a digital caliper and it claims to be the size it states it is.

It was waaaaaaaaay easier blowing compressed air in this to break the fluid seal than trying to pry it off.

The tool works but if you're a fraction off, the tool tip is very slippery. There was a point where I was struggling to get the shim out and the tool slipped off of the bucket, and thankfully the shim was still there...all I had to do was push it back into place. If it wasn't there I think the bucket would have pushed against the cam and I wouldn't have been able to get the shim back without taking the camshaft off and messing with the timing.

The angle of attack in getting the shim out was incredibly tedious and frustrating, until I eventually tried some fingernail tweezers, and that worked a hell of a lot easier.

Also re-seating the shims is a pita, they don't like to seat perfectly, and I might be off by a fraction, and trying to push the shim in there to make sure it seated properly, one time caused the bucket to slip off the tool and push up against the cam. When I go to rotate the cam back to remove the tool, there's a POP as it seats into place. UGH. Stop making noises I do not like that

Now I can order what I needed to order

 

I was able to take off the carbs, with some difficulty. I had to unscrew all of the bolts that held in the air box, and I finally have the carbs off, however, at least four of the screws that are holding on the rail on both sides, are frozen. So I had to buy a a impact screwdriver, and I'm going to try that. Because some of the screws are starting to be stripped.

 

The impact screwdriver does not seem to be helping, so I may need to drill them out or something. Not sure what I can do at this point

 

JIS screwdrivers before you start. (Probably a bit late)
Dissasemble the carbs (keep everything in separate areas for each carb) and apply some heat to the body where the screw is going in.
Hold them in a vise, gently so to speak.
Cut a slot in the head and use a flat big tight flat blade or get a really tight grip with vise grips and give it a tap to unstick ccw.
Drilling out as a last resort.

They are pretty soft heads so the jis screwdrivers are really ideal before starting as normal Phillips is close but not quite dead on.

 

I have been using JIS but these screws on the rail are stuck.

Also will probably need to replace this brass bolt too, it was stuck and soft...

Can I hit it with a few seconds of map gas?

I've pretty much torn apart carb #1 and it's in the ultrasonic with dawn dish soap, but I can't get any of the others out

 

Definitely. Just get all the meltable stuff away, basically.

 

Sweet! I'll do that tomorrow or Saturday.

Look how clean this is now!!

 

Also, what the hell happened to this shim that it looks like this??

 

Is this a "STARTER PLUNGER VALVE"? Since it's slightly has stripped edges on the bolt, I'm considering replacing it. Why the fudge is this brass???

 

That's a weird look. They are hardened tool steel so pretty tough. Maybe a grain of something hard stuck under it?

 

Keeping this for my records and also thought this was a really informative video on what goes where for rebuilding the XJ650 carbs. AI voice is a bummer, but it seems super helpful of a resource!

 

Question: if I find a decent 750 maxim tank, that doesn't have a gas cap or a petcock, I should just be able to transpose my 650 maxim's petcock and gas cap, right?

 

Dan Gardner made a copy of the original.

If you have access to the XJCD you will be able to check part numbers.
https://beerfueledmayhem.github.io/xjcd/PARTS_DIAGRAMS/parts_menu.htm

 

I don't know what XJCD is, but I can take a look at that link. What does "made a copy of the original" mean?

 

XJ650J looks like the petcock assembly is 4H7-24500-01-00
XJ750J looks like the petcock assembly is either:
33M-24500-00-00
or
15R-24500-00-00

But on the xj4ever HCP626 item claims it works on XJ650 and XJ750 models, so I'd imagine the original petcock would fit, logically anyways that makes sense.

The gas cap assembly seems to have the same part number:
4X7-24602-00-00

edit: I ordered it, it looked like it was an almost mint condition 1982 750 maxim tank with the sending unit included, which is a huge boon because I'm gonna replace this instrument cluster one day and I want that damn low fuel warning, lol

 

I'm thinking about getting the Oil Cooler in a few months, but if I am remembering correctly, the horn would be directly behind the oil cooler, has anyone relocated the horn? Would probably take some fabbing, I guess?

 

If the horn is in the way I vote for the oil cooler

 

I believe you can have both, I just was thinking in my head I'd like to relocate it.

Besides that, it's in the way of doing a valve clearance, and if I'm gonna be doing that every 5000 miles, it's one extra annoying bit of the valve clearance process I'd rather avoid in the future. I think once the shims come in I'll probably do a valve clearance again in 500 miles, just because I'm OCD and this bike is old. (and then of course in 5000 miles after)

 

I'm not going to name my bike until I've finished doing the valves and the carbs and she's running again, the valves aren't going to come in until Monday, which means next weekend.

But the name just came to me randomly as I was driving home from work. So I googled the meaning of the name and it's absolutely perfect.

"Sensha" 戦車 (tank (military) or chariot)

 

Hello RideAlong420, newcomer here. If i remember correctly, you took your rear brake pedal out. I bought my own Yam 650 xj 4 KO not so long ago, and cant really figure out how the rear brake pedal with the brake rod was installed. Cant really find any pictures online, so i figured i might just ask here since the thread is fairly active. Would you kindly jsut send some photos , how the whole shebang is connected to the frame? Thank you.

 

The rear brake pedal is extremely easy to remove. It's just held in by a bolt and a nut and then you just pull it off. I can take a picture tomorrow but it's really straightforward

 

I couldn't remember what jets are in the carbs, but someone before me changed the exhaust to a 4->1 and xj4ever says you can safely update the jets, even if you're stock, to #41 & #112 so I ordered those for when I break apart the carbs.

Some of those screws are really stuck in there (on the upper and lower rack rail), so I'll hit them with some MAP gas and hopefully the aluminum will expand enough for me to take the screws out without needing to re-thread anything. Carb 1 looked fine and nothing was cross threaded, that I could tell.

The butterfly valve...rod thing that holds the round wafer thing, whatever that's called, looked like it had some clear hardened gunk on the hole that at first I thought was aluminum from overtightening or cross threading, but the gunk congealed and came off after I took it out of the ultrasonic cleaner (just 100F water and some Dawn dish soap for about 1.5 hours), so I guess it was just old loctite gunk or something.

I'll be upgrading every screw on the carbs to hex, to help future me. I'm also upgrading the float needles to metal instead of rubber tips, due to how much ethanol gas there is around. Those gaskets on the float bowls were extremely hard and brittle.

I'm also replacing the fuel line since it's extremely hard and brittle, and putting an in-line filter, along with replacing the vacuum hose, which the end started crumbling as soon as I removed it from the petcock.

Shims aren't gonna show up till monday which SUCKS but oh well.

I'd really like to take the exhaust off so I can sand off the flaking black paint, but those exhaust studs look extremely rusty and I'm nervous to snap them off, having to tap and drill anything on the bike makes me anxious.

 

Try loosening the exhaust nuts and see if they are stuck. If they were tightened to the right torque, they will not be that tight. Rust, however, still lock them on.