Diagnostic Help: Buell Blast

I think I need a little help diagnosing a problem on my roommate's Buell Blast. It's a carbureted single-cylinder, and it's having trouble with cold starts.

We just installed a new auto enrichener this afternoon and the problem still persists. This is supposed automatically bypass the throttle butterfly so that the bike idles a little faster while it warms up. There is no choke of any kind on the bike.

Symptoms: If you can get it to start (which involves cranking the starter with the throttle cracked open ever-so-slightly), the engine pops, skips, and misses like crazy until it gets warm. You have to hold the throttle open a hair to even keep it going. Once it's warm, however, it's like a brand new bike. It idles peacefully, it quiets down, and the throttle response is what you'd expect from the bike.

When my brother gets it started, he immediately revs the E36 M3 out of it to keep it running (I prefer the finesse of just keeping it running). This CAN'T be good for the thing because the cylinder isn't lubricated. Did doing this damage the rings? Could this explain why it only works well when it's warm?

Whadda you guys think? We really want to get it working right because she wants to sell it to buy some sort of European thingy (Triumph Triple ). It only has 4,000 miles on it!

The rubber boot holding the carb in place is super sensitive to cracks , any will make it run like crap.

I'd definitely hunt for air leaks. IIRC both Buells and Harleys run pretty lean as is and any air leak is going to make it worse.

BTW, if the carb has an accelerator pump, I'd give it a couple of twists of the grip to see if that improves starting.

jefmed2, I will check out the rubber sleeve you speak of. We never thought of checking that!

BoxheadTim, it doesn't have an accelerator pump. I wish it did (and that I knew what that even was).

You guys don't think it is the engine itself, do you?

You certainly have a problem in the cold start mechanism, whatever it is for that carb. No, the engine itself is just fine. Check for intake leaks by warming it up, get it idling, then spraying a little carb cleaner or WD 40 around the intake area and listen for changes in engine RPM. Although, if it's doing fine when warm, I'm thinking that's probably OK and you just have a bad/plugged up cold start system. I'm not familiar with whatever carb is on there. There has to be some kind of choke/enricher on there or you'd never get it started.

confuZion3 wrote: BoxheadTim, it doesn't have an accelerator pump. I wish it did (and that I knew what that even was).

It's a mechanism by which the carb dumps additional fuel into the airstream if you wack open the throttle quickly. They're usually integrated into the carb itself so unless you know what to look for you don't spot anything out of the ordinary.

My FXD had one, hence my comment.

confuZion3 wrote: You guys don't think it is the engine itself, do you?

Nope, don't think so. Carb issue or air leak, something's weakening the mixture.

The blast uses the Keihin Constant Velocity carb.

Be sure and check the rubber boot on the carb as Jefmed says, I blew mine up 2 weeks ago. The part is 13$ and might be worth buying and replacing. You aren't going anywhere if that boot is wasted, ask me how I know? Even if it looks good it can be broken along the clamps. If you ride the bike and let off the throttle and the thing backfires you have air getting in past the air box.

Check the stupid stuff first like that the fuel tank spigot is on "on." Then you might want to check the jets, don't know how, they are only 6$ per jet though.

I have the manual but it is at my house and I'm visiting my mom right now. I can give you more information next week when I get home.

I wouldn't worry about ruining a blasts engine I've been trying for the last 5 years and it still runs.

I have the same problem...auto enricher replaced, plenty of fuel (cleaned carb) new spart plug...still doesn't want to start when it's cold. Would the boot affect that? It runs great when it's warmed up but the only way to get it started when it's been sitting a while is with a little squirt to the carb...

If it looks like this, you've got a problem. That still pisses me off a bit. Cool little bikes.

So weird that people with clean bikes have issues keep their bikes running but my 3 times crashed is the charm, 30k miles blast has never refused to start for me. It even kept running after each crash in a show of solidarity.

What happens when you crank the engine? Does it smell of fuel out the exhaust? Have you pulled the airbox and verified fuel is coming out of the jets? My 3000mile guess would be either the carb boot is dead, you are sucking too much air or if you have modified anything the bike can be running very lean. From the factory they are tuned for emissions and if you put an aftermarket exhaust/intake you need to go up a step in jet size for each mod. I'm running 1 size over on both the slow and fast jets and think I could go up another size. There is an idle adjustment screw on the carb, but you might have to drill out the plug. Just be careful because I adjusted my mixture before and had the plug fall out on the road, had to order a new one for 40$. The rule of thumb when you adjust the mixture is the bike should respond as you open and close the adjusting screw. You basically tighten the screw all the way in then back it off I think 2-3 turns. If your idle doesn't change keep backing the screw off until something happens. If you are too far out of spec for adjustment you need to rejet the carb to the next size up, then you go through the mixture adjustment process again and you should be within spec for the amount of turns on the mixture screw. You don't want to have to adjust the mixture too rich as the plug will fall out, the mixture screw is only for fine adjustment.

This is how I tuned my bike so I probably did it incorrectly but my blast still runs like a raped ape so this is first hand experience.

benzbaron wrote: my blast still runs like a raped ape

I have never heard a Blast described as being remotely fast

Grtechguy wrote:

benzbaron wrote: my blast still runs like a raped ape

I have never heard a Blast described as being remotely fast

Then you've not been to this page. http://sidewayspromo.com/buell_blast_racing.htm

confuZion3 wrote: Whadda you guys think? We really want to get it working right because she wants to sell it to buy some sort of European thingy (Triumph Triple ). It only has 4,000 miles on it!

how much for the bike?

PM me

For anyone who may read this in the future it was the low idle jet... Despite a good first cleaning it was evidently still plugged up. Up and running great again :-)