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Re:2004 Roadstar blowing carb off manifold
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TOPIC: Re:2004 Roadstar blowing carb off manifold
#1019768
Hopcycle (User)
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Re:2004 Roadstar blowing carb off manifold 3 Months, 1 Week ago  
Curt wrote:
SVS is caused by bad jetting. In my experience get rid of the hokey Hypercharger and get a real true air filter like a K&N filter. Rejet your carb to better jetting and remove the air jet that the HC calls to be installed. I had a HC long long ago and had many problems like you and I developed a SVS cure which the guys use. Got rid of the HC and rejetted my carb and all was good for many years to come. There are to many places for air leaks on the rubber boot on a HC and the air/fuel value changes to much and to be honest all they are is something to try and impress people who know nothing about bikes to start with. Just my .02 and if you need any information that used to be on my site just PM me you e-mail address here. here.

I read many threads referencing your cure but all the links were broken. I'd love to have a copy of your technique. I'll pm you my email and thank you!
 
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#1019774
texasscott1 (User)
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Re:2004 Roadstar blowing carb off manifold 3 Months, 1 Week ago  
I don't think the same results can be obtained rotating the engine by hand that are occurring when the engine is running. The lifters will tend to collapse when the pressure of opening the valves is applied. This whole thing could even be a timing problem but to me it's just too much of a coincidence that it all started again after the work you did.

Good luck
 
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#1019821
ultrastar (Moderator)
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Re:2004 Roadstar blowing carb off manifold 3 Months, 1 Week ago  
Just out of curiosity when you tore down the motor did you mark the pushrods because they do have to go back in the exact same way they came out
 
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#1019833
ctkog (User)
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Re:2004 Roadstar blowing carb off manifold 3 Months, 1 Week ago  
When the heads were off did you by chance inspect the valve-guide clearances? Comparing an early year repair manual I have to my '08 manual there was a change resulting in a .0004" increase in the exhaust valve-guide clearance (went from .0006" min to .001" min). I don't have an 04 manual to see if it also lists the tighter clearance but no matter what manufacturing could have still missed their proper clearances on it.

If all else fails, since you comfirmed SVS it might be worth going back in to re-inspect those clearances, and if needed hone or ream the guides to achieve .001" minimum exhaust clearance. If you measure yours at .0008" -.0009" you're probably going to be fine since the old minimum was .0006, unless you have something else going on like a slightly bent valve. Don't rule out intake clearances as an issue either. Check them all.

I certainly hope you find a different cause, like finding a timing issue or something else. There's nothing worse than having to go in and repeat work, other than not fixing the problem.

best of luck
 
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#1020296
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Re:2004 Roadstar blowing carb off manifold 3 Months ago  
Good morning Gentleman. Sorry for the delay getting back. It took a few days of working on other bikes in shop to free up a chance to get back to this one. Despite the leakdown test showing valves sealing, I decided to tear back into the rocker boxes after removing exhaust and witnessing that the rear cyclinder valves were barely moving as I spun the engine. I found the issue. The brand new sealed power lifter for the rear cylinder exhaust has failed. when I performed the top end refreshen I was unaware of the SVS issues that Yamaha had on the 2004 models so I didn't ream valve guides, just cleaned and hand lapped valves and seats. Inspection of carb and it's jetting shows it hasn't been addressed and my theory is the rear exhaust valves began sticking again and ruint the brand new lifter. I've ordered the 6mm reamer and intend on pulling head, reaming guides and when assembled and running put on my dyno and dial the carb in. Thanks to all for your input! Great site here!!
 
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