1982 xj650rj seca tuning

Okay, So after my rebuild, i've gotten the bike to run and occasionally can get it to hold an idle. However, intermittently it will rev straight up to 5-6k on startup. Hinting at a vacuum. leak. This video below was taken 20 minutes before my high idle started.



Plug 1


Plug 2


plug 3


plug 4


I've recently taken the carbs to church. Full teardown. breaking the rack, soaking each carb in carb dip for 2 hours, rinsing off with hot water, replacing all seals, and new jets. Replaced the carb boots with OEM items purchased from Chacal (not the cheap ones that tear instantly). From this post i've got a few questions to help get her back and running perfectly:

1. Feedback on the plugs? they've got maybe 5 minutes of run time on them.
2. From the video, shouldn't the carbtune be reading a higher vacuum amount? (i thought on my xj650 maxim, I was getting higher amounts)
3. Potentially thoughts on the sudden 5-6k idle? My potential thoughts are:

3a. Vacuum caps on carb boots. I have new rubbers on them, but currently do not have the clamps installed. Proved to be too big of a pain to get those on.
3b. Airbox lid seal. I've noticed that 1 corner of the airbox has a slight "lip" on it that doesn't appear to be a complete seal. Would you believe this would explain the potential airleak to cause a rev that high?
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Any other thoughts are appreciated. Looking forward to getting her back on the road after 5 months.

 

Have you performed a running (vacuum) synch yet? If not, start there!

 

Like with the carbtune? Yes I've done that.

 

Did you wet-set the float heights?

 

Yes I did. Even retested on the bike to make sure that none were too high and they are all good.
On that thought though, with the new front end, the front sits lightly lower than stock. Based on this, should I adjust the wet set level of the carbs? Instead of being 3mm from the bowl top?

 

1. Are you sure you have the air jets in the correct places? Bigger number toward the front of the bike, smaller number toward the seat of the bike.

2. Check to see if your pilot jets have been drilled bigger

3. Make sure your cables aren't kinked

 

Air jets are in correct places.

Pilot jets have not been drilled bigger. Unless Chacal is secretly drilling them

Cables should be good. But i'll double check. I know that the throttle cable snaps back, but i'll double check the choke cable and the throttle.

 

Is it fully seated in the carb bracket?

 

Yes I even get a little slack on the carb side of the cable just to make sure that it wasn't an issue. Once she's dialed in I'll adjust the cable slack to a better spot.

 

I would say yes the readings should be higher, and what you have is almost useless to do a proper sync when you consider the bouncing. I don't have a Carbtune Pro, but I am guessing that first of all the dampers / restrictors are not present, which may attribute to the low reading as well as the unsteady readings.

1, 2, and 4 look sooty, but only 5 minutes the engine was likely still on choke so I don't think it means much and you need to wait until you get it sorted to do a proper plug color evaluation.

I would go through the pain to be sure they are sealing particularly since the high revs may be a result of a vacuum leak. Seems I remember you can put the clamp on the cap and then just push the cap on. Not so easy getting off though on a hot motor.

 

Your Bike looks great... See your running CB750 Coils ..Two thumbs up, got them on my Seca 750.

 

As Rooster said,

Make sure you have restrictors in your Carbtune vac lines, or you will get low readings as have....

Make sure those vacuum caps have clamps on them....it is not that hard to get them on.....put the clamp on the cap, & you should be able to push them on.

 

Carbtune levels should not matter as long as they are even... with that said - I agree with Rooster (and your own initial observation) - something ain't right there. Any chance of another bike (you still have your Maxim?) in the neighborhood that you could hook the Morgan up to?

 

I have seen people hang ( and I have hung ) the Morgan Carbtune upside down as well for sync'ing.......might give you a better shot at sync'ing.....( the rods will drop into the gauge further )...give it a try....

But make sure you have restrictors in your vac lines.....

Just sayin....

 

Thanks guys! I thought something was strange since the last time I did the carbtube. I even remember holding the bag of resistors and thinking, do I need these? Haha it was right under my nose.
Okay, I'll hopefully try to Resync carbs on Tuesday and install the clamps on the caps too. Thanks again!

 

I believe there is a couple of sets of restrictors in there, so use the smallest ones...it will work better for the readings......if you don't have the restrictors, you can borrow my Carbtune.....

 

Thanks! I'll let you know if I run into issues. Glad there's another xj rider in San Diego

 

So i had some extra time today after work and took the carbs off to check a few things. I noticed that the fuel levels after doing another wet set test were a tad low. I'm currently re-adjusting these now. Hoping that by going over the carbs yet again, i can get everything dialed in perfectly. Hoping to not have to take the carbs off the bike again

 

One thing about float level , I flip carbs over measure from flange with no gasket set from tip of float set it at 17mm ... then check wet set this gets you in the ball park. On mine this was spot on.

 

I tried that approach and got some very inconsistent fuel levels. So I've gone with the longer method, check each float level and adjust. And repeat until it's in spec.