Rebuilding EJ255 - does my plan make sense? - Page 2

Glutton · 11-13-2022, 09:56 PM

What does wiseco recommend for clearance? A forged piston needs a lot more than stock clearance. Honestly, my mind is blown at attempting these measurements with feeler gauges anyway. You can get pretty decent mics and a bore gauge for just a few hundred dollars, and it will go a long ways to having a reliable engine.

* Registered users of the site do not see these ads.

motorbykemike · 11-14-2022, 07:31 AM

the rod ratio on a 2.5 79mm crank is 1.65

with a +2mm rod it goes to 1.67 , not really noticeable

you really start to see the difference on a 75mm crank with 2mm (1.77-1.78 deepening on what "2mm" rod as they are all different) or 4mm (1.8)

the real advantage to using the 2mm rod on a 79mm crank is the piston weight is lighter

BipBoby · 12-04-2022, 01:41 AM

I put everything together and measured such bearing clearances:

Rods (ACL bearings)
1 0.0015"
2 0.0015"
3 0.0015"
4 0.0018"

Crankshaft (King XPG bearings)
1 0.0015"
2 0.0015"
3 0.0018"
4 0.0018"
5 0.0018"

What do you think about those measurements? I know they are not ideal but at this point I have to say I am a bit tired and would just go with it. Let me know what you think.

I have some extra STDX main bearings, so in theory I could make main clearances bigger but I don't think that's the direction I should be going.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

11-13-2022, 09:56 PM	#26
Glutton Scooby Newbie Member#: 529499 Join Date: Apr 2022	What does wiseco recommend for clearance? A forged piston needs a lot more than stock clearance. Honestly, my mind is blown at attempting these measurements with feeler gauges anyway. You can get pretty decent mics and a bore gauge for just a few hundred dollars, and it will go a long ways to having a reliable engine. * Registered users of the site do not see these ads.

11-14-2022, 07:31 AM	#27
motorbykemike Scooby Specialist Member#: 273868 Join Date: Feb 2011 Chapter/Region: MAIC	the rod ratio on a 2.5 79mm crank is 1.65 with a +2mm rod it goes to 1.67 , not really noticeable you really start to see the difference on a 75mm crank with 2mm (1.77-1.78 deepening on what "2mm" rod as they are all different) or 4mm (1.8) the real advantage to using the 2mm rod on a 79mm crank is the piston weight is lighter

12-04-2022, 01:41 AM	#28
BipBoby Scooby Newbie Member#: 530531 Join Date: Jun 2022	I put everything together and measured such bearing clearances: Rods (ACL bearings) 1 0.0015" 2 0.0015" 3 0.0015" 4 0.0018" Crankshaft (King XPG bearings) 1 0.0015" 2 0.0015" 3 0.0018" 4 0.0018" 5 0.0018" What do you think about those measurements? I know they are not ideal but at this point I have to say I am a bit tired and would just go with it. Let me know what you think. I have some extra STDX main bearings, so in theory I could make main clearances bigger but I don't think that's the direction I should be going.