First Cafe Racer Mod! 1983 XJ750 Maxim

I think your earlier assumption of regulator/rectifier might be correct. In my experience, when the solenoid clicks but the starter doesn't spin, your battery voltage is too low. Depending on your specific model, one of the wires on the reg/rec (brown on 82 xj650) is looking for voltage to provide appropriate charge. This wire MUST go through a switched connection otherwise it will be a parasitic drain on your system.

 

This might be correct, but that's a big assumption to make. And Aaron, how did you get to "my solenoid is faulty"?
You just shorted it out and your starter didnt spin! That means either your starter is duff, or your battery is duff, or the connections from batter to earth, or battery to solenoid, or finally, maybe solenoid to starter are bad.
Charge and check battery, check batter high current connections, short solenoid (if it doesn't pull in). Starter should spin over. I wonder if your battery was low all the time, and the solenoid stuck on (does happen), further draining the battery (sometimes setting the bike alight too).

 

I’ve taken care of the battery by using a smart tender that shuts off when done, when testing it looks good too.
I tried jumping the solenoid and nothing happened so I replaced it.
I also tried jumping the starter and again nothing happened, this was all right after firing it up but granted I was holding the START button for around 10 seconds to get that initial spark.
I did take the starter apart and check all the specs and it appeared to look fine, but since it wouldn’t spin I ended up buying a new one from @chacal.
I’m hoping I just burned it out by holding it too long since I didnt make any significant changes to the wiring especially that have to do with its ability to start.

 

I jumped the solenoid as recommended after it had the issues by placing a screwdriver onto both bolts of the solenoid.

my battery looks strong and connect med negative to the body and positive to the bolt.

I hope there’s no more surprises!

 

ha ha ha, that was a good one

 

Having issues with syncing carbs now...
Hogfiddles rebuilt my carbs so I know they’re good but when I have my Carbtune Pro setup as instructed and I try dialing in the screws, no matter what I do it starts revving up to 5-6ooo RPM’s!

I can’t even tell what tightening or Loosening the mixture screws do or even the idle screw...
Can someone clarify what the direction of turning screw and idle mixture does to the bike, manual doesn’t explain that simple piece

I have to keep turning off the bike to prevent engine damage.

what should I be inspecting???

•New intake boots on both ends of carb, new valve cover gaskets and rubber bolt things
•Shims inspected and replaced

Variables:
•It’s on center stand
•Stock headers, no muffler (eventually Mac 4-1)
•K&N stock air filter replacement, big one from Chacal
•#124 main fuel jets and #43 pilot fuel jets
• live in Chandler, AZ elevation = 1214

 

Turning the mixture screws IN leans the fuel mixture.

The idle SPEED knob needs to be backed out almost fully.

Choke is off, correct? Choke plungers closed?

Throttle cable isn't hung up on the cylinder head, preventing throttle from closing all the way?

Is it "instantaneous" 5-6K rpm's or it just builds and builds and "runs away" and so you finally shut it down?

 

Turning the mixture screws IN leans the fuel mixture.
-Now I know!

The idle SPEED knob needs to be backed out almost fully.

Choke is off, correct? Choke plungers closed?
-Yes it’s off, barely needed it to start.

Throttle cable isn't hung up on the cylinder head, preventing throttle from closing all the way?
-It’s actually quite loose.

it just builds and builds and "runs away" and so you finally shut it down?
-That’s exactly what it’s doing!

 

Building RPM's usually happen when warming up the engine with some enrichment (choke). As the engine warms and the RPM's climb you would normally adjust the lever to bring them back down. If you are not using any enrichment lever you might want to double check the plungers.

 

This is a typical situation with an engine that is out of synch.

By the way, just to clarify, when using the Carbtune synch gauge, you do NOT adjust the idle mixture screws, you will be adjusting the SYNCH screws (located on the throttle brackets, between each set of carbs). Once you get the engine stabilized and "in synch" (the sliding metal rods on the Carbtune gauge at equal levels), only then do you start fiddling with the mixture screw (using a Colortune plug, hopefully) to adjust the pilot fuel mixture screws....which, in the process of adjusting those, will also throw off the engine synch a bit, and so the Colortune and Carbtune processes are typically done "in tandem" with each other: colortune a cylinder, adjust the engine synch; now colortune the next cylinder, and re-adjust the synch, etc. Anything that affects the power output of one cylinder alone (such as, adjusting the mixture screw for that cylinder) changes the power output of that cylinder (relative to the others), and thus results in the engine being "out of synch"----the power output of each cylinder is unequal, and thus the engine must be re-synched to bring cylinder outputs back to an equal level.

The Carbtune gauge measures the power output of each cylinder using the strength of the vacuum draw from each cylinder as a "surrogate" way of determining the power output of a cylinder; this is why the synch gauge uses resistive springs over each sliding metal rod; they apply a pre-set level of resistance to each rod, so the strength of the vacuum draw in each cylinder can be "measured" by how far the vacuum can pull the rod up. There are many factors which determine why a cylinder might have a greater (or lesser) vacuum pull than others (fuel supply, piston ring seal, valve adjustment (i.e shim clearance), etc.). But whatever the reason(s), the purpose of synch is to equalize the vacuum draw (power output) of each cylinder:

https://www.xjbikes.com/forums/threads/82-xj-650-startng-problem-surpise.46358/page-2#post-414262


Also, this why an out-of-synch engine will experience this type of run-away engine speed............one (or more) cylinders are fighting for "domination" over the others, and in the process using more and more fuel (= more rpm's). One cylinder has a much greater vacuum draw than the others, and "vacuums" more fuel out its carb, and this starts the run-away (that's why it slowly builds and then goes into a runaway situation, the other cylinders can't counteract the dominance of the one great, almighty cylinder which is controlling the idle speed and so the rest of the cylinders are just "along for the ride" with no counterbalancing effect........).

 

Wow!
That’s pretty interesting! Then would it be a good idea to “lean out” all of them, turn them out maybe 2 turns and then adjust from there to at least get them somewhat close to each other?

 

So I leaned out the adjustment screws and then put them at 2 turns which made syncing easier but it’s still doing something weird...
I got #1 to flutter closely to #2, I matched #4 to #3 but when I start matching 1/2 to match 3/4, it starts revving up again when they’re getting close to each other and when I press down on the adjustment screw (middle one) with the screwdriver it brings the idle back into reasonable range but then they’re all mismatched again while pressing down to control the idle runaway.

 

use the idle knob to bring it back down.

don't do dat, that's just wrong in so many ways, use the idle knob

 

It doesn't respond to the idle knob at all...

 

your sync is in left field then. two ways to get it back, pull the carbs or
unhook the TCI, hook up you charger, turn the idle knob in till it hits the tang then two full turns more, hook up your sync tool, crank it 5 seconds and see what you got, then do the 1/2, 3/4, thing
but only 5 seconds on each set so be quick and don't be to picky close is good, feel the starter, hook the TCI up, start it it's going to race, use the idle knob
if that idle knob ever stops working, make it work