| Author | Message | ||
     Bluv21 |
Hello THUMPer Land, As far as my set-up for a stock Blast I have: -Shimmed the needle 0.05" -45/170 Jets -Idle mixture screw turned out 2.5 turns -adjusted primary chain by ear method -new spark plug. checked connections I am still getting slight flat spots in the throttle. that harder I roll on it, the more pronounced the flat spots. Any other suggestions on fine tuning? New ignition module perhaps? Any input appreciated | ||
| Ezblast |
Try the idle mixture a 1/4 more out, then if that still happens, loose one shim - still happens - try 46 primary. EZ | ||
| Bluv21 |
Thanks EZ, I reckon I'll try that. I tried a full 3 turns out on the idle mixture but it really didn't like that plus there was a fair amount of fuel in the airbox. I know a little is fine though. | ||
| Bluv21 |
One other question. If I am forseeing installing a V&H exhaust, should I still go through those steps or should i leave the same set-up except up the main jet to a 175? | ||
| Gearheaderiko |
If you V & H, leave as you have and bump up to the 175. You can add less or more shims too. 2 shims is a guide or like all recommendations, a place to start. Your spark plug is gapped correctly? New? You havent changed anything else on the carb such as changing or modifying the slide spring or drilled any holes? Is the vacuum port on top of the carb in front of the boot plugged? Some carbs may not have this port as it is only used in CA bikes. Gas tank properly vented? | ||
| Bluv21 |
New spark plug gapped to .04. Nothing else changed on the carb that I did. Only the shims, 45/170 jets, set the float between .413 and .453 as specified, new float bowl gasket. By the vacuum port i assume you mean the float bowl vent? Also how do i verify if the tank is vented properly? | ||
| Gearheaderiko |
Not a float bowl vent. Its on top of the carb, near the back, right before the boot. The picture near the bottom of the intro shows the location: http://www.badweatherbikers.com/buell/messages/201 64/6812.html?1333890182 To check to see if the tank is properly vented: Loosen the gas cap while running-tank is now vented (dont do it with a full tank or gas will spill everywhere). Blow through the vent tube-is it clear? If you stop the bike and pulling off the gas cap produces a rush of air (hiss), then you know its not venting properly. Did you change the float setting or just check it? | ||
| Bluv21 |
I may have bumped the float when I changed the jets so i measured it with a caliper from the flange surface to the top of the float at about a 17 degree angle from the normal plane of the manifold side of the carb just to be sure it was right. It was about .53X when I measured it so I reset it back to the .413-.453 as specified in the manual. It ended up being .43X. I was sure to get the caliper as close to the float surface without depressing the float. The vent tube is the tube running off of the top of the tank forward of the gas cap correct? I am just trying to iron out the slight flat spots in the throttle response. EZ recommended checking the idle air adjustment and maybe going out 2.75 turns. | ||
| Bluv21 |
Gearheaderiko, Which is the port you are talking about? Here is a clipping from the service manual that shows the manifold side of the carb.  | ||
| Gearheaderiko |
Its a nipple on the other side of the carb, on top. Your carb might not have it. | ||
| Bluv21 |
Yeah I don't think it has it. This is a Florida bike. I have taken the gas cap off just after running the bike and have not noticed a hissing sound but I will double check. Any other ideas that have outside of what EZ has recommended? | ||
| Gearheaderiko |
Yes, thats the tank vent tube. As far as the float adjustment I can't get my head around whether you increased or decreased the fuel availability by adjusting the float to where you have it. If the float adjustment wasnt altered by your bumping it and you decreased the fuel availability by re-adjusting it, that can cause a flat spot. (I'm sorry, its tough to concentrate while I'm trying figure out random meaningless tax code that doesnt make any difference but I need to get it right so I can file my taxes.) | ||
| Bluv21 |
Ah yes, taxes... Only 2 things constant in life... Death and taxes and laundry.. ok maybe 3. Anyway, according to the service manual, decreasing the measurement (i.e 0.53X -> 0.43X) will increase the amount of fuel to the bowl. The thought crossed my mind too so that's why I double checked it. The flat spots are slight but I cant figure out how to iron them out further. I haven't tried EZ's suggestions yet but I will go through them methodically | ||
| Gearheaderiko |
EZ's the CV carb king. You might want to check the timing too. uh...what air filter are you running? If your carb doesnt have the nipple, there will be an aluminum plug where it should be or just a flat round spot for the hole to be drilled. But its real easy to miss the nipple and the rubber cap tends to crack over time. | ||
| Bluv21 |
Hmm I will have to double check that when I get home. Is it on the butterfly valve side like i have posted? and I have a stock airbox with a K&N replacement filter. | ||
| Gearheaderiko |
Opposite side where the boot connects. Airbox okay! I just wanted to be sure you werent running something creative or different which can affect airflow. | ||
| Bluv21 |
Ah ok so the intake manifold side. So this would be in the top of the carb and should be plugged? Also, I was just reading the service manual about timing. Is this method accurate? If I understand correctly, the vertical mark should come into view indicating TDC (with the assumption that I am in the "ballpark" when air stops coming out of the spark plug port). The module plate is then rotated until the LED illuminates. Although I think the Manual is wrong and it is not pointing to the correct module plate screws.  Is this a correct assumption? (Message edited by bluv21 on April 09, 2012) | ||
| Gearheaderiko |
The arrows are a little off, yes!!! But the rest of the procedure is right. Mark the module plate location and if you dont get the LED to light, rotate the engine one full turn. | ||
| Ezblast |
If you look at the carb pic above, that black dick sticking out is the capped vacuum line - ok - now everyone laugh - lol EZ | ||
| Gearheaderiko |
LOL! Well, I just learned something new. Apparently the nipple (lol) can be either in the location noted above, or just before the boot on top, or non-existent. I had previously thought the bd position was only on the twin carbs, but after pulling a Blast carb off the shelf, voila, there it is! My apologies. | ||
| Sycho |
Erik, I sent you a PM. Just wondering if you are in So. Cal. or Montana? | ||
| Bluv21 |
Well in that case, yes there is a nipple (aka weinus) on the carb and yes it is capped. Another question on the timing. Do I really need to get a new timing cover? I read on the instruction forum that you can take it off using a thin blade and you do not have to drill a hole. Are there any issues I hsould know about to get the existing cover back on? Thanks! (Message edited by bluv21 on April 10, 2012) | ||
| Bluv21 |
Anyone have an idea if I can reuse my timer cover? | ||
| Ezblast |
yes - till it falls off. EZ | ||
| Bluv21 |
How does it attach? I have read that you can get it off with a thin blade but I couldnt find how to get it back on... | ||
| Gearheaderiko |
PM sent. | ||
| Jetlee |
lol ... mine flew off while going down the road. Never did find it. |
