Calling all porting pros, check these pics!
Posted: December 3rd, 2012, 6:43 am
Here's my story: '86 engine just rebuilt the motor from the crank up and compression is only 125 psi (know protocol and used two different testers). Also passes all leak tests, new top (and bottom) and bore (1.5 over). Pulled cylinder after only 1.5hrs of ride time and cylinder wall/piston all look good - no scoring, blow by, etc. And while the bike is hard to start (know protocol) it otherwise seems to run strong, unboggable, no detonation, etc.
I continued to pull the jug and it looks to be very tinkered with, so my question is: Could the relieving of the exhaust port/bridge to such a degree (or any of the other porting) lead to the compression being so low, ie 25%+ from the norm? And as the work looks unevenly done (on all bridges), by perhaps another amateur mancave mechanic, does that even matter?
Is it recommendable to reduce the squish clearance and mill the top of the jug and head, perhaps up to .5mm total (ie .25mm each)?
Appreciate any feedback from the porting pros, upon looking at the photos. Thanks in advance!
![Image](https://bannedcr500riders.com/images/auto/fe21108b3574613001a4a2e135352760.jpg)
![Image](http://i1280.photobucket.com/albums/a500/kenzonut%0A/exhaustbridge.jpg)
![Image](https://bannedcr500riders.com/images/auto/4bb9ae103fe14bd5839108a90faf0498.jpg)
![Image](https://bannedcr500riders.com/images/auto/43fdfb17214eb5168c347399400bfbb0.jpg)
![Image](https://bannedcr500riders.com/images/auto/605f4f72c575e2336a694afad1793658.jpg)
I continued to pull the jug and it looks to be very tinkered with, so my question is: Could the relieving of the exhaust port/bridge to such a degree (or any of the other porting) lead to the compression being so low, ie 25%+ from the norm? And as the work looks unevenly done (on all bridges), by perhaps another amateur mancave mechanic, does that even matter?
Is it recommendable to reduce the squish clearance and mill the top of the jug and head, perhaps up to .5mm total (ie .25mm each)?
Appreciate any feedback from the porting pros, upon looking at the photos. Thanks in advance!
![Image](https://bannedcr500riders.com/images/auto/fe21108b3574613001a4a2e135352760.jpg)
![Image](http://i1280.photobucket.com/albums/a500/kenzonut%0A/exhaustbridge.jpg)
![Image](https://bannedcr500riders.com/images/auto/4bb9ae103fe14bd5839108a90faf0498.jpg)
![Image](https://bannedcr500riders.com/images/auto/43fdfb17214eb5168c347399400bfbb0.jpg)
![Image](https://bannedcr500riders.com/images/auto/605f4f72c575e2336a694afad1793658.jpg)