1340 evo upgrade question
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5th Gear
Joined: Jul 2010
Posts: 9
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1340 evo upgrade question
I'm about to get my feet wet for the first time with my 80incher. I have 2 broken off exhaust studs that i need to repair and i told myself that if i ever had to tear into the motor that i would consider beafin it up a little. How much can i bore it oversized and what will i have to replace without making it unsafe?
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
You cannot increase the bore by very much. That is a limitation of Evos, compared with twincams. It ain't possible to make a 124 out of an Evo, except by buying a brand new aftermarket motor! You can stroke one to 89 inches, or stroke and bore to about 106, but IMHO that is also pushing to the very limits in size.
People like HDF sponsor Hillside have ways of tuning a 'small' Evo to give excellent performance. Scott may pass by here, or you could give him a call. He could probably repair your head and port them at the same time!
People like HDF sponsor Hillside have ways of tuning a 'small' Evo to give excellent performance. Scott may pass by here, or you could give him a call. He could probably repair your head and port them at the same time!
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
If the bike has a high mileage and you tune the top end, there is a risk the bottom end may not last very long, under the increased power. But a bottom end rebuild starts to get expensive! So there are economy questions to be resolved. I stroked my original evo to 89 inches (with a rebore it became a 90!) but when I wanted even more I eventually bit the bullet and bought an S&S 107. So beware! If the bug bites things can get expensive.... 
Road Captain
Joined: Jun 2008
Posts: 640
Likes: 13
From: Hickory, NC area
This is a great question and one I seem to mull over daily. I really like my 80 and it runs perfectly fine. I'm not poppin wheelies or anything, but it has plenty of power and with my few simple mod's it gets great mileage, is generally reliable (although messed up right now) and has sufficient power. HOWEVER, I really would like to be able to pop wheelies - even if I don't I want to know I can. But it seems like running the engine until it is tapped out is the smartest thing to do. It has 45k on it now and so one would expect somewhere in the next 50k to need to do a major overhaul. Until then, it is just a waste of money to put too much into an engine I am going to either swap out for the 107 or 113 or rebuild with the 96 kit.
So, to the OP, I might suggest fixing that stud and getting whatever miles you can out of it until you are ready to bite the bullet and do the whole deal. Then you can choose between boring/stroking, adding bigger jugs, or buying an aftermarket engine to stuff in there.
Just MHO.
So, to the OP, I might suggest fixing that stud and getting whatever miles you can out of it until you are ready to bite the bullet and do the whole deal. Then you can choose between boring/stroking, adding bigger jugs, or buying an aftermarket engine to stuff in there.
Just MHO.
Tourer
Joined: Mar 2007
Posts: 462
Likes: 1
From: Arizona
Broken exhaust stud why open motor?
Why do you need to get into the motor for broken off exhaust studs? I drilled out the old stud (drill bit and easyout) then installed a new one. My old 80" had over 200,000 miles on it without ever being opened. When it did go south, I replaced it with a 100" RevTech. I just burnt a hole in the aft piston and can't get another. (back ordered) The Crane High 4 apparentlly malfuntioned and through the timing off = hole in piston. Over 65,000 on that motor. Now that was an excuse to by a new Ultima 107". Looking forward to getting her back on the road.
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