Hayabusa requires 10% throttle to run after replacing head gasket

[hezekiahmunson]

Hi, I have a 2005 Hayabusa with a Hahn turbo setup on it. It ran great other than leaking pressure into the coolant last year, ran 152mph 1/4 on 6 psi. To fix that I replaced the head gasket and also installed a base spacer while doing it. I installed the cams back in standard, so about 3 degrees retarded I guess with the spacer in.

The problem is I got it all back together and it takes about 10% throttle to get it to start and keep it running, and it surges back and forth very rhythmically about 200rpm. The AFR looks good around 16:1 low down, fuel pressure looks good around 40psi. Doesnt want to rev up. I disconnected the Power Commander and still same problem. I checked for vacuum leaks and dont see anything, no sensors unhooked. It runs smoothly other than the surging back and forth, no missing, I disconnected a plug wire and it instantly got choppy and missing, so seems to being firing correctly and smoothly.

Could this be result of the cams being put in completely wrong, or does it sound more like a bad sensor somewhere? I checked and double checked the cams, I put them back in exactly the same way as they came out, marked them and didnt turn the engine, but I didnt degree them.

Any ideas would be greatly appreciated! Thanks!

 

[sixpack577]

There's lots of sharp turbo guys here, someone will be along with your answer.

 

[hezekiahmunson]

Thanks. Im thinking it isnt a turbo thing but something else. Im wondering if the cams being mistimed could do this, or would it just not run. Thinking back on it, I was thinking I'll put them back in as they cam out, but I didnt have it in gear when I pulled the cylinder block off to put the spacer on, I bet I spun the crank a little and changed the crank timing, then put the cams back in as they were, but now the crank was timed differently. Hmmmm, Ive been messing with this for hours and this just dawned on me. :duh:

 

[GMbusa]

Sounds like a vacuum leak. Check your lines and intake boots. I bet one intake boots has folded in. It's easy to do. Also, check the small vacuum lines for one to of popped off.

 

[ssober]

I would guess vacuum leak also.

 

[smithabusa]

check vacuum line running to the map sensor

 

[hezekiahmunson]

Thanks for all of the replies, it definitely ran like a really bad vacuum leak, I checked and checked and looked at everything over and over, finally came to conclusion Im a moron and the cams have to be mistimed. Turns out the intake cam was 2 teeth retarted, exhaust was 1 tooth retarded, so 17 degrees on intake and 7 degrees on exhuast retarded and it doesnt run so great. I got a shop manual and discovered there is the cam timing inspection cover where you can see the little mark on the starter clutch you can check it on, it would have helped if I had a shop manual originally. After timing the cams it started right up and runs perfectly now.:stoopid: