| Author | Message | ||
     Simonbg |
My wife's Blast was in hibernation for 5 years after the famous rocker gasket started leaking oil all over her legs and due to life change event - it was neglected. The good news is, I got it running and it runs great...but the cold start is rough - at least it is back to what it always has been. The best way to describe this is "anti choke": Bike starts with very low RPM and needs to be helped with the throttle for 30-45 seconds. After that it stays running, barely, with RPM gradually increasing. In my estimate, it probably runs 700-800rpm first till it goes to what sounds normal (1200) 5-7 minutes later. I spent 3 weeks reading service manual, posts, and work on the carb. I thought it is the auto enrichener, which I fully understand is not a choke. So I did very serious investigation: Got the carb out and applied external voltage and watched (thru the top, needle assembly removed) the enrichener plunger closing the hole within 4-5 minutes (I was applying 9volts, could be faster on the bike it is supplying 13v). Then I let it cool and it retracted. At my starting point, the top hole was covered about 30%, I adjusted that to 15% (meaning providing supposedly more fuel when cold, aka "increasing choke"). I also opened the carb top black cover after 10 minutes idle run to confirm it is functional on the bike - it is. Didn't help. What else can cause this slow cold RPMs? From what I am reading, it should be the other way around - starting with faster rpm and gradually decreasing. Here is a list of everything I have done this year: *Replaced rocker cover to head gasket with metal, rocker cover top and inner. *Cleaned carb - got it starting with a bit of a fluid and chocking intake port *Replaced idle jet with #45 (from 42) *Replaced main jet to 170 (from 165) *New Velocity Needle from CVP *Cleaned the carb again *Discovered enrichener has it's own permanent jet which is way up high in the bowl. Cleaned that as best as I could, cleaner sprays passes thru it with big stream. However, I was not able to pass any wire thru it (I think the path has almost 90 degree angles). ^^^after this step, it started starring without choking intake/sprays but dies if don't help it with throttle *Since the enrichener jet is way high in the bowl, I adjusted the float to allow a bit more fuel - it is right at the border of the specification per service manual (although measuring that is tricky) *Replaced the carb to engine boot *New fuel lines and fuel filter *Filled up the tank with fuel system cleaner, just in case. *Cleaned the carb again *Service manual talks about possibly too much carbon buildup - I sprayed Seafoam carbon cleaner as directed and also let it soak over night. Changed the oil the next day. *New Iridium spark plug *Cleaned the carb again ***I have idle mixture thumb screw on order but the old one seems fine. Bike is almost stock - original air box but with K&N filter; Stock exhaust, NON California model. I want to emphasis that as far as I can remember, it always had rough cold start. The only other thing that was ever done to it (many years ago) was replacing the ... ?ignition module? that is inside the right side crank case cover - it had the common fail to start when hot issue. I am not the first owner. | ||
| Gearheaderiko |
If this was 10 years ago I could’ve told you exactly what the problem is, but alas time has clouded my brain function. Why did the previous owner sell it? Since it looks like the ignition module was replaced, I would check the timing. Since you’ve had the carb off multiple times you might have seriously fouled it up. Is the TPS mal adjusted? Why did you replace the needle? Is it compatible with factory jets? Is the bike “choking out” when you first start it? Did you replace the boot with a OEM replacement boot and you’re sure it’s not leaking? You replaced with factory carb jets not jets for another aftermarket set up? What happens if you unplug the TPS/throttle enrichener and run the bike? This can really help in diagnosis. Factory spark plug gap? Given that it’s sat for 5 years, you’re not the original owner and given that I’ve seen a lot of horrible incorrect advice posts on other sites (BWB is fairly accurate, but there was a poster or 2 giving out really bad advice), we’ll have to cover some basics, again. | ||
| Simonbg |
Thanks for your reply. Is the bike “choking out” when you first start it? - if I don't play with the throttle (continuously adjusting it) it will die; sometimes it back fires and smoke comes out of the air box (only within the first 60 seconds) The jets and needle are from a reputable source - CVP. I replaced the needle because reading advises here to shim the needle, for slightly better performance. The replacement supposedly addresses that and it shouldn't affect the cold start/idle anyways. The boot is OEM. Spark is NGK Iridium as mention in first post. The bike runs really well. It can start on it's own(without touching throttle) as early as 90 seconds after warm up but RPMs continue to increase till full warm. I have not tried starting it with TPS/Enrichener disconnected yet - will try today. I have not adjusted the TPS - reading the service manual about the TPS at the moment. I want to emphasize 2 things again: Engine performance is back to where it was or is better before the hibernation and I am happy where it is except the cold start. Engines starts/idles fine after warm up.} (Message edited by Simonbg on May 24, 2022) | ||
| Gearheaderiko |
Just trying to figure out if your AE is actually working properly. Unplugging the electrical plug to it and the TPS can tell you a lot about how it’s working. As far as carb changes it’s much easier to diagnose a bone stock carb than a carb with a bunch of changes to it. You’re going from the known to the unknown, especially if not using factory parts. Many many carbs have been fouled up by good intentions. The most common is “giving the carb a good cleaning”. It rarely needs this. Carbs have different running circuits. So it may run just fine in a couple areas but fail miserably in one or 2 others. (Generally-start, idle, quarter throttle, mid range, WOT). | ||
| Simonbg |
Update on this: The start up improved on it's own, not sure if it was the fuel additive, the now warmer weather, or the engine got cleaned up by giving it the beans. The AE is 100% working as I opened the carb top cover after operation - it was closed. To start the bike now, I simply open the throttle and crank. But I have to help it with the throttle for 20-30 seconds, else it will die. It also may backfire or sputter during these initial 20-30 seconds. I am still waiting for my new air mixture screw (got lost in the mail), so I can't really tune it anymore until it arrives. As to the "“giving the carb a good cleaning”. It rarely needs this " - I've read these exacts words in many forum threads here, probably all yours. My tip is - you haven't seen a dirty cab  (Message edited by Simonbg on June 04, 2022) | ||
| Gearheaderiko |
I’ve seen many many carbs and resurrected a lot of motorcycles and cars. Giving the carb a good cleaning is basically saying pull your engine apart and give it a good cleaning- you’re basically hoping it fixes what you don’t know is wrong. It’s usually just a clogged low speed/pilot jet (on a Blast that’s been sitting). “Give the carb a good cleaning” usually translates to “I don’t know what’s wrong, but I hope that fixes it”. What I have seen, a lot, over and over, especially online, is inexperienced people messing up perfectly good carbs by taking them apart under the misguided advice to “give it a good cleaning”. If you know carbs, you’ll know if it actually needs cleaning/rebuild. Mostly they have a specific fault and that’s what needs to be fixed. I wish I had a dollar for every time I’ve pulled a carb off the shelf and slowly disassembled it to try and figure out exactly what a poster had missed or messed up based on their description of what they did. | ||
| Gearheaderiko |
Make sure your timing is correct. Static timing or with a light (making sure it’s timed at the right rpm’s). It you’re having that much pre ignition, something is wrong. Blasts are not naturally prone to it. A common cause by new Blasters is lugging the engine like it’s a V-twin. Blasts need to be revved out and don’t do well on low rpm torque. You’ve got a lot of changes going on, I’m just trying to help you sort things out. |
