PDA

View Full Version : New Rebuild Back firing.. Need Help


bcapien
12-19-2009, 02:14 PM
OK heres the deal.. I just did a rebuild on my 400ex and here is the list of upgrades..

Weisco 416cc kit
Hot Cam stage 2 cam
Edelbrock Signature Series Carb
AMR stage 2 cdi and monster Coil
Full HMF Exhaust

So i went to fire it up today and started great then back fired.. Started again and same thing..Now its back firing from the front of carb. Checked the timing and its on 100%.. I think its running really lean so i am going to try adjusting that but what else would cause this?? I have checked all valves and no leaks.. Nothing is bent or damaged.. Could it be that its not getting the proper amount of fuel?? The fuel line seems to be a bit to long so i am going to trim it up and see if that helps.. Any help would be great.. Thanks
bcapien
12-19-2009, 04:33 PM
bump
CSR400EX
12-19-2009, 06:28 PM
what is the compression of the new piston, and also did you add all the upgrades while it was apart?? it sounds like you need to richen it up. one good thing about edelbrock is that they are easy to tune
bcapien
12-19-2009, 10:27 PM
11:1.. And thats what i think.. Seems like its not getting the proper amount of fuel.. Yes i did all the upgrades at the sametime.. Its starting great just tends to back fire and die out.. Then starts up great and samething again.. I think its pulling to much gas and back firing or just running very lean.. The carb is for a 440ex but with all my upgrades i should be ok.. I will try again in the morning.. Thanks
CSR400EX
12-20-2009, 07:43 AM
also, did your edelbrock carb come with a choke or enrichment circuit? if not they can be a pain to get them up to temperature. i had one without a choke and you had to keep it running or else it would die out until the motor got up to temperature
bcapien
12-20-2009, 09:01 AM
no there is no choke or anything.. I have also been reading that HMF has had issues leaking around the header at the head so i am going to check that also.. I am on my way there so i will post what the problem was.. Bad thing about doing all the upgrades at the sametime is its not good to just let the bike rev and idle after rebuild.. So i dont really want to just let it idle to temp..