The title about sums it up... i've got this 2000 Honda Ace Shadow Deluxe, which is a 750 twin-cruiser, with a pair of Keihin 36mm carbs on it. The history is not good (it's my sis's bike) It developed some issues, and she took it to a shop. This was a couple years ago, but it hasn't been ridden but once since then... They cleaned the carbs, charged her $400 and sent her home. The problem was a stumble or flat-spot midway up the RPM range, such that the bike would actually quit running just about when you wanted to shift. The shop did not fix the problem. So, it sat at my house (outside, but under cover) for a year at least, when i tried to start it again. Sure enough, it would start on the battery! Wow! It needed some "choke" to idle though. I have since learned that the choke on these carbs is not really a choke, but an enrichment circuit.... About two months after i started it, we went to send it home and... no start. Would fire nice on ether/carb cleaner though. After trying the pour-in carb cleaner stuff, i gave up and pulled the carbs, which was not as bad as i anticipated. There was crystalline gunk in the float bowls.. one had a lot and the other had a little. I removed the jets, used a piece of fine copper (soft...) wire and a lot of carb spray to clean the two removable jets (big one, little one), generally sprayed the heck out of the rest of it and found that there were four small holes near the throttle plate, cleaned those off. These being covered with goo is probably why it wouldn't idle w/out the enrichment/choke earlier... Anyhow, now it's all back together and it starts and idles like a dream. But it bogs fatally with any throttle at all... even if i try to run it up really slow, it dies around (guessing, no tach) 3000 rpm. It's BAD.. not rideable at all. I've searched far and wide, and can't find any information about tuning/setting these carbs other than how to swap jets etc.. Obviously i just want it to run right so i can get it off the front porch and my wife can be happy. ;-)
You are gonna need to a little more work on the carbs. Sounds like munge on the needles or in the tube around the needle. Right above the main jet. Carbs will probably need all the air passages cleaned. Are these CV carbs? Could be the diaphragms are shot as well. If the vacuum passage to the diaphragms is clogged, they won't raise the pistons and the needle therefore won't come out of the main jet, leading to the bog/stall you are experiencing. Might want to contact the Kehin distributer and see if they offer a rebuild kit. You'll still need the carb cleaner and maybe some pipe cleaners for the passages. Make sure you have a working diagram or take lots of pictures as you dismantle.
Thanks... I was afraid of that, since of course i've got sand in my shorts and don't wanna pull the carbs again... These are indeed CV carbs, and the slides appear to work fine, like they should. I'm pretty sure the diaphragms are ok. It's likely as you say, gunk on the needle or in the tube. Feh. I'm a luser for not doing a better job the first time.. I can't find any markings or model numbers anywhere on these carbs (except "keihin"), but web sources tell me they're 36mm (looks about right) There is only one externally adjustable point on the carbs other than the thumbscrew that sets the idle (by opening the throttle blades), a small slotted screw low on each carb. I'm guessing this is the idle mixture screw? When i turn them both all the way in, the idle goes shitty.. it seems happy with 1/2 to 1 turn out on both sides. Are there any other adjustments? Do these carbs need to by synced? I used to have some old SU carbs that needed syncing... thanks again for the great help!
ANy multi-carb setup needs to be synced, but as shovel stated the carbs need more work. Were it me, I would take them to a shop that can hot tank them. As long as they have been sitting there si going to be gunk in places that are very hard to get to and leaving the carb bodies in a vat of cleaner for a couple days works wonders.
Try a carb sync first (the 99-cent carb sticks work great), but it sure sounds like you've got a bigger carb issue than that. I miss my '02 ACE. Great bike. Don't give up. Once it's running, it's a CHAMP, and you'll never have another problem as long as you ride it regularly and store it properly. Several guys have rolled over 100,000 miles on them. Also, check the air intake boots for leaks. It's possible you could have a leak around one of the carbs. Ditto with the air filter mechanism.
It appears to be all fixed now... it'll need a longer ride to tell for sure. [THANKS for the guidance!] I took the carbs back off, and cleaned them again. I did find a bit more crystalline gunk in one of the bowls (came down from on top of the floats?), but really nothing notable other than that. As before, I used only carb-spray, no dipping. All of the rubber (there are two diaphragms per carb, and one o-ring besides the bowl gasket) was fine, new-looking and feeling. Some random observations: -- Getting the carbs back into an ACE is a royal biotch. Those short boots are not very flexible. The trick seems to be to put it in twisted a bit while straddling the bike. Push HARD and twist them straight; both boots have to go on at the same time. -- The ACE is a fat-bottomed-girl in every way. I'm not ashamed to be seen riding her. -- When backing out of the garage for a twilight test-ride, that tinkling you feel on your leg may be from the tank-valve you just flipped open while pushing back. If you forgot to put the fuel line back on. -- I had previously tested before with the old spray-the-vacuum-lines trick. I used carb spray, and did see a rise in RPM but i suspect that was merely because the intake is so close to where i was spraying (the boots, and other vacuum lines). Ether seemed a bit foolhardy, but probably would have had a more notable effect when/if it hit a leak.
