650 Mod's 78 Fighter Build

Awesome, Steve! Thanks! I guess that's true seeing that we might get a handful of days into the mid 30's (celsius) compared to how hot you're used to on a steady basis. I'll be sure to get some pictures up of the plugs when in.

Devin

So Christmas came in July! This showed up yesterday, so today I made a run down to the border store and picked it up. You know you're in for good parts when the parts are Japanese made The Suzuki petcock and B7ES plugs both from Z1. Nice quick shipping.




Next step was to drain the tank and get the old petcock out. Old one on the left, new on the right. The Suzi one definitely is a little smaller and tidier. I had to rotate the vacuum line 90 degrees to point down so that it would hook up to the vacuum line on the bike.



After making sure I had no leaks on the tank, or on the lines/filter, it was time to fire it up. Here's how I ended up running the fuel line to clear everything. The bend was too tight to come right off the tank and go inside the frame, so I had to loop it around the frame just under the tank and above the side cover. I double checked that there wasn't going to be any rubbing or pinching, it's all good. This picture is with the tank raised slightly.



Looking from the rear of the bike forward, the line then makes a 180 degree slow bend and cuts down between the wiring loom under the seat.



Lastly the fuel filter is hooked up and the line sits at around 40 degree angle. Fuel flowed fine at this angle, there was no issue with starvation or anything under hard acceleration.



Fired the bike up to make sure it was going to pull ok, and all was well. Out came the B8ES plugs and in go the B7ES plugs. I was kind of nervous about making a step in the heat range of the plugs with all the engine work I've done to the bike, but so far so good. Minus one thing... That friggin somewhat rich condition is still on cyl #2 even after the petcock change... Which leads me to think that it is a leaky valve letting some oil burn. Or a small carburation issue I can't find (after endless cleans with cleaner and compressed air, etc).
Went for an 8 mile/12km ride to see what the plugs would look like. I know, not enough of a ride to really get a view of how things are burning. But enough to colour the plug tips to let me see what I might have to do. This is cylinder 1-4 from left t right (regulator to clutch side).



All 3 "good" cylinders are burning a light tan right now like this.



Overall, some of my issues have been sorted out- that mid range burble isn't there anymore (or as noticeable), and the throttle response is MUCH better under all RPM ranges. The petcock was SUPER simple to install and mounts right up. The part that took the longest was figuring out how to snake the line in place in order to avoid snags and kinks.

Other than that, there's one more issue sorted out on the bike for me now. I think I might have to pop the valves out over the winter and re-do the seals to be safe. Unless anyone has any other tips on where this rich issue on cyl #2 (vacuum line cyl) is coming from.

Devin

Try leaning out #2 with the screw.
Steve

Steve- #2 is turned pretty well all the way out before the spring loses tension to keep the screw in place. I've had it like this since I tuned it up this spring. I'm stumped...

I was reading in to carbon fouling, and these points come up:

Air/fuel mixture (A/F) too rich (I have the screw as lean as it can go before falling out)

Incorrect adjustment of carburetor

Faulty auto choke system (Cleaned and oiled choke sliders last spring, nothing is catching now. Maybe something is sticking internally?)

Faulty fuel injection system (not applicable here)

Faulty electrical system (Shouldn't #3 also foul this way if the coil is on the way out?)

Poor connection of high tension cables (cables are new with the coils (2 years ago) but I could have an issue on this one. I have new lines, I just need to get some coils to run them into- can't with the ones I have as the spark cable is epoxy'd in place)

Inadequate running conditions (Not sure what wouldn't be ideal on just that one. Everything has been balanced and tuned the same)

It is necessary to run at higher speeds (about 80 km/h) from time to time. (I ride it like I stole it, no issue here haha)

Prolonged idling (definitely doesn't happen here)

Continuous low speed driving (Again, doesn't apply. Even at slower speeds I try to keep engine speed up when possible)

Too cold a spark plug (Not applicable- switched back to B7ES)

Air cleaner contaminated (Doesn't matter what pod goes where, it still does it).

Sorry for the wordy post... Just trying to get this thing sorted out.

Devin

I'd try screwing it in until it starts to falter then out a touch. To fine tune my air screws I take it up to 2500 or when I hear a miss then dial it out. Could be a bad HT wire or connection.
Steve

Steve- i'll give it a shot and see what happens. I have that colour tune unit too, so i'll run that again. Any other ideas? I'll probably do the could over the winter to run some new ones. Thanks Steve

While it's true if one plug doesn't fire on the same coil, the other won't either. However, if there's a bad connection or plug, the other plug will look good while the trouble one won't. Bad resistor caps can do it too. I've hardwired to the plugs to rule that out.
Steve

All 4 plugs are fresh and it still did it. So if what you're saying is maybe the culprit with the wore- I could switch the leads from cyl 2/3 to see if it follows to cyl 3. What do you think?

Yep, try it.
Steve

650mod wrote: All 4 plugs are fresh and it still did it. So if what you're saying is maybe the culprit with the wore- I could switch the leads from cyl 2/3 to see if it follows to cyl 3. What do you think?

Since it's the #2 cylinder I would test the vacuum line from the petcock (I assume you're using a vacuum operated petcock - if not ignore this reply). If there is a problem with the diaphragm in the petcock fuel can flow through the vacuum line into the #2 carb and cause a rich condition. One easy way to check this is to put a clean spark plug in #2 cylinder; disconnect the vacuum line from the #2 carb and plug both the vacuum port on the carb and the petcock vacuum hose; and then run the bike with the petcock in the reserve position. If the problem goes away the petcock is at fault. If the problem persists you can rule pretty much out the petcock as the source of the problem. Ed

Steve- will do, chief! Short and simple tester to see what happens.

Ed- I just replaced the entire petcock unit yesterday with a new replacement one (brand new) so I ruled put that being the issue. I had issues with it before doing the same but wet fouling when I ran the stock petcock. Checked the line for kicks last night after the new petcock was on and it's dry.

Which leads me to think it's a spark plug cap, lead, or coil. I'll swap #2/3 leads to see if the issue follows it.

Thanks for the tips guys!

Devin

How is #2 carb holder?
Steve