XJ650RJ Seca Build

Carb synch?

 

I spent some time with the carb sync and the colortune yesterday. I can get the bike to idle nicely at around 1000 rpm and fully warm up. After some throttle pulls holding the throttle at around 4K for a few seconds the bike takes some time to return to idle. 6 or 7 seconds. If I push down on the sync adjustment screws I can sometimes force it to drop quicker. Then on some throttle pulls it will just stay at 4K rpm.

The throttle cable and encroachment cables are not binding. Only thought I have is either my throttle shaft seals are bad (that I just replaced last year), or the carb butterfly plates aren’t 100% flush in the bodies.

I might have the carbs rebuilt by hogfiddles so elminiate any chance of a carb issue and allow me to focus on other issues. Air leaks

 

LOL, this has to be the best compliment.

Thanks for sharing the progress. You have a beautiful bike.

 

If it was the butterflys then you wouldnt be able to sync it properly. what are you use to sync the carbs? If you have starter fluid laying around, try spraying it on the boots and carb and see if the bike rev's up. You might be suprised where the leak is coming from. I had a leak on an outside brass washer that i didn't find till i sprayed starter fluid on it and the bike rev'd high.

Also you might want to check your plunger diaphrams and make sure there arent any holes

 

hogfiddles is in the process of going through my carbs now. So this will make sure that everything is 100% on the carbs.

While he has these, I went through my valves again and noticed that my exhaust clearances were all off. I assume when I last did them I had the book in front of me, vs looking at the inside side cover which had the correct specs. (or some other brain fart). So now that those are done, once the carbs get back I should be in a better starting point to get everything working 100%.

As far as syncing tools, I own the Morgan Carbtube, and the Gunson colortune which I have used for all of my syncing thus far. I've also done every trick for trying to find leaks, starter fluid, electrical cleaner, unlit propane.

Lets hope that all of my issues were due to the carbs not being 100%, and the valves being done improperly.

 

Check your manual to verify .11-.15mm intake, and .16-.20mm exhaust

 

Good choice, he does great work.

I know Dave has them now but upon reading this it is possible to get the sync screws wrong when reassembling the rack preventing the butterflys from closing all the way. Also could be plates not put back in correctly aligned.

Either way you;re in good hands, keep us updated on how it goes.

 

I'm waiting to see what hogfiddles says I had wrong with the carbs. Always trying to learn from past mistakes so that I don't make them again.

After the bike is working as it should, it's time for some new rear shocks, and then wrapping the exhaust pipes. Until I have a pile of money for phase 2 of the build.

 

So after a few months away, I was able to get the carbs back on the bike. Shortly after that, my battery crapped out. Since replacing that I have gotten a few hundred miles on the bike.

After some fun riding through the mountains, I've noticed that at freeway speeds, I get a little bit of a weave on the rear end. At first, I thought it was tram lining, but always thought that my swing-arm could be at fault. When i originally did my build, i took the swing arm off to have the frame powered coated, but did not replace the bearings. I'm also not sure that I tightened these to spec, so I'm wondering if I could have over tightened them which made the swing arm stiffer.

I did a test after removing the shocks, and could not get any movement on the swing arm side to side or forward, to show that the bearings were bad, however upon removing the bearings, from the swing arm I can see wear marks. So I will be replacing these tomorrow when the new ones come in the mail.

 

So what was up with the carbs?

 

I actually ended up trading carbs with hogfiddles. He mentioned that my rack had bad fuel valve seats, and that I left one of the tiny rubber washers in the fuel enrichment circuit which caused an air leak in that carb. But after getting the “new” rack on my bike everything works well. (Minus the enrichment circuit). So I’ll clean that out one day

 

What a heck of a saga! I'm in the midst of a rebuild on a 82 Seca, just finishing reassembling the engine after tracking down transmission problems... the reason the bike was parked for a few years and ultimately became mine. I have pretty good experience with twin carbs on British cars and so as not too concerned about these 4 side drafts, but after reading your tale I'm preparing for some adventures in tuning!

 

Do you still use stock rear wheel? If yes, how wide tyre you got fitted there? if no where did you mount the wheel?