carb rebuild problems

[kennethleemiller]

Hi everyone..

Some of you may remember me posting, last month that I was rebuilding the carbs on a 650EX. At that time I got literally a truck load of info from several of the veteran GS experts here, and I am extremely grateful for all the additional references.

That said, I have finished the rebuild on my carbs and after scouring the net (ebay) and eventually acquiring two replacement bodies and various other bits and pieces which needed replacing, I have finally reassembled and installed what should be a fully functioning rack of carbs. The problem is they hardly function at all.. :/

I have followed the rebuild guide as provided by Ed Ness to the 'T'.. all the way up to and including the bench sync. The only step I have left to accomplish in is the vacuum sync. And there inlies a problem. I can't even get the bike to stay running long enough to warm up the engine, much less get an accurate vacuum reading to set the sync.

I bought the Dynojet Stage 3 kit for these since I am running open element filters, notice I said open element and not pods. I bought the K&N RC-2382 dual flange open filters (which I highly do not recommend)!! I got these because of how close the frame comes to the mouth of the carbs. This filter appears to be thin and very easy to install as opposed to how far out pods would project when installed. In fact, the RC-2382 filters (though the K&N website lists my bike specifically as a fit) are extremely hard to get on the carbs and, when installed, touch each other and the frame. I plan on switching to pods, but am still worried that the #1 and #4 will touch the frame. But that's a different story. Since I have the open filters and stock exhaust, Dynojet recommends the .155 main jets, which I currently have installed.

To me, the engine seems like it's flooding. When I go to do a cold start, the engine will turn over two or three times and then start to try and fire on it's own, and it will sit there and kind of half way fire and start to turn itself over (with the assistance of the starter) for a while, I would estimate 20 to 40 revolutions (starter assisted) before it finally gets up enough momentum to keep itself alive while the throttle is just barely cracked open. After this, I have to keep the throttle at this barely cracked position to keep it running, but the engine eventually just fizzles out. If I open the throttle any higher, it just dies. If I return the throttle to idle, it just revs down to nothing and dies. Last night while keeping it alive with the barely open throttle trick, I reached under and started cranking up the idle position to try and keep it running without me holding it, and eventually topped out the idle screw with no effect on the rpm. After it dies I have to wait 15 to 20 minutes for the chambers to dry out before I can even attempt to try starting it again.

I have tried making adjustments to the air/fuel screws, but this seems to have no effect on the problem at all. I'm really at my wit's end, and I don't know where to go from here.. Tonight I plan on removing the carbs and doing another tear down and rebuild just to see if maybe there's something I've missed. I have no idea what it could be, for when I did this the first time I went page for page through the tutorial.

If anyone has any suggestions, ideas, comments... It would be greatly appreciated..

Thanks,

Ken

[spyug]

Sounds to me like the carbs are not properly clean and your battery is weak. Its having trouble cranking her over and supplying enough juice to fire the plugs.

I would have those puppies off and strip them and dip them for a minimum of 24 hours. Rebuild with fresh o-rings of course.

When first putting fresh carbs back on it helps to have a booster battery as sometimes you need to crank them a bit to get fire & you need the aforementioned juice to fire the plugs.

I would also junk the airfilters until you get it running, they are just another distraction for now. To add a little air restriction you can cover the mouths with some cling film (Saran wrap) with a little hole in the center.

Once it fires and runs you may find that the carbs start puking gas but don't be alarmed. Remove the film and that should stop. don't worry about running with out filters either but do put them on when you are ready to do the synch.

If you are still having trouble getting it to run then I'd suggest dialling back the jets to stock and working up to a larger jets in steps. The advised jet size may not be right for your application. Trial and error is often needed in situations like this.

Good lyuck with it.
Spyug

[kennethleemiller]

Thanks Spyug, perhaps they do need a longer dip... I initially did a 2 hour dip on these which is an hour longer than recommended on the dip can.. I'm really nervous as to the length of time these carbs spend in the caustic solution.. It's always been my assumption that motorcycle carbs are pretty delicate by nature..

I will try a longer though..

[koolaid_kid]

Tell us how you set up the kit, the instructions are not on DynoJet's site. Mains, pilots, needle position would all be good information to help solve the issue.

[cowboyup3371]

24 hours is what these carbs need to really get cleaned up good.

[kennethleemiller]

Tell us how you set up the kit, the instructions are not on DynoJet's site. Mains, pilots, needle position would all be good information to help solve the issue.

Yeah I've been down that road too, no instructions online, and my kit conveniently didn't come instructions either.. I had to call DynoJet and sit on the phone with their jetting engineer to find out what size main jet to use..

Kit came with a set 160 and 155 mains, air correctors, needles, glue, a small punch for installing the correctors and two different drill bits. One to remove the air screw cover, and a smaller one to bore out the air return hole on the bottom side of the slides. No pilots and no springs..

I used the 155 main jets, glued in the air correctors, drilled out the slides, and set the needles on the third notch from the top, which would be the fourth notch from the bottom.. and that's it.. there weren't any springs or pilot jets to replace, and I actually inquired about that while on the phone with DynoJet and they specifically told me they were not required for this kit.

[tom203]

" I'm really at my wit's end, and I don't know where to go from here.. Tonight I plan on removing the carbs and doing another tear down and rebuild just to see if maybe there's "

I spend lots of time at wit's end- and it's a very crowded place. Anyways, even with the wrong jets/ wide open intake stuff it should at least start (but run ugly) IF the "choke" system is not plugged. With all throttle plates basically closed (bench synched), cranking with "choke" activated pulls fuel up from bottom of bowls, throws some air into it, and it fires. It you're just cranking away, something/many things is/are plugged. When you reclean them, make sure the little passage from bottom of carb bowls to carb body is clear.

[kennethleemiller]

" I'm really at my wit's end, and I don't know where to go from here.. Tonight I plan on removing the carbs and doing another tear down and rebuild just to see if maybe there's "

I spend lots of time at wit's end- and it's a very crowded place. Anyways, even with the wrong jets/ wide open intake stuff it should at least start (but run ugly) IF the "choke" system is not plugged. With all throttle plates basically closed (bench synched), cranking with "choke" activated pulls fuel up from bottom of bowls, throws some air into it, and it fires. It you're just cranking away, something/many things is/are plugged. When you reclean them, make sure the little passage from bottom of carb bowls to carb body is clear.

Will do, and thanks for the advice.. I notice you also have a 650 and, being that you're a senior member, you may be just the person to answer another question... Are the heads all models of 650s interchangeable? In other words, if I find an old 650G head and rework the valves, could I use it on my 650E?

Thanks,

Ken

[recycled64]

650 heads

As long as you match the appropriate engine # range, the heads will interchange- go to www.babbittsonline to see what I mean- has to do with the # of valve cover bolts, 16 vs 17, extra one at the front of the cam chain tunnel. Unsure what you mean by reworking the valves, they're the same across the board, E vs G.

[hikermikem]

Welcome to the forum... those E model (chain drive) 650's are a bit of a rare beast. Nice bike for sure.

Those carbs need 24hrs in the dip to get properly clean.

Good luck getting this sorted, might be frustrating to find the proper set-up for those pods/stacks.

[tom203]

Will do, and thanks for the advice.. I notice you also have a 650 and, being that you're a senior member, you may be just the person to answer another question... Are the heads all models of 650s interchangeable? In other words, if I find an old 650G head and rework the valves, could I use it on my 650E?

Thanks,

Ken

You'd think so, but as recycled64 said, the camshaft cover got a extra bolt half way thru 82 model year.The bolt shows up in cam chain tunnel at very front on opposite side from tach drive. The valve timing on E's was different than shafties.

[kennethleemiller]

Attached a photo of the finished carbs, after 24hr dip and re-rebuild... and I also went ahead and polished the caps and bowls, and put a couple of layers of rosso red on the bodies.. hopefully I can get them to perform as good as they look.. I think my problem is the sync.. I need a better way to do a more precise bench sync so I can get the thing running well enough to hook up a vacuum... As far as pods are concerned, I'm leaning towards a set of UNI PK82's or PK92's.. not sure which ones would fit the mouths better.. anybody every tried these??

[hikermikem]

Wow, those are sure purty!! Nice work !!

For the bench sync, simply hold the rack of carbs up to a light & open each butterfly until only a sliver of light can be seen shining through. It's easy enough to visually set them all the same... this will get them very close to being properly sync'ed.

Not a lot of positive feedback here on the UNI's. The preferred Pods are K&N, but i believe Ape offers essentially the same for much less money.

[kennethleemiller]

For the bench sync, simply hold the rack of carbs up to a light & open each butterfly until only a sliver of light can be seen shining through.

So Friday afternoon I stopped by a local mc salvage yard to pick up some extra bowl drain screws, and was talking the guy behind counter, who gave me the same advice on holding up a light to the back of the carbs. Worked out pretty good and after that routine I checked using the small wire method and I think I've got them sync'd close enough to where it should start well enough to do a vacuum sync..

That's the good, here's the bad:

The guy talked me out of the extra screws, which I was going to use to make a set of four spouts for the clear hoses to do a side by side level check, since last time I just had one, and had to drain and reattach to each and measure individually.. I should have just followed my instinct because the method he talked me into ended up being way messier, and not as accurate.

He also told me that my problem was not the sync, that it was the jet size. He said the 155's that came in the dynojet kit were way too big, even after I tried to explain that numbers between Mikuni and Dynojet are not a direct match..

I've heard nothing but good things about this dynojet stage 3 kit and I just would like to hear from some of you, who are experts on these bikes in particular and not just a guy that knows a lot about bikes in general. What is the answer here? Do I need to ditch these and go smaller, or stock, or somewhere in between??

I just don't get it.. If I can't get it to run right with the modifications I've made up to this point, I'm afraid I'm going to have to just take it somewhere and tell them to do whatever it takes, which I really don't want to do. I feel like I'm right on the verge of getting this thing to run like new..

I haven't tried starting since this last dip and rebuild.. I'm going to hook up the tank and try tonight..

I'll let you guys know what happens..

[kennethleemiller]

Just some more thoughts on this... I'm my mind, and someone please correct me if I'm wrong. The size of the main jet should not matter for the first 1/2 to 3/4 turn of the throttle. In other words, for the purposes of starting the bike and low to mid range control, the main jet isn't even use. Right or wrong?? The function of idle to 1/4 throttle falls on the pilot jet, right?? I mean even if the main jet is too large, would you even be able to tell if you can't get the throttle out of idle range??