Rethinking Bottom End
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Outstanding HDF Member
Joined: May 2012
Posts: 2,385
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From: Brentwood
Rethinking Bottom End
So I just got my bike dynotuned and I’m fine with where I’m at. My thought before getting the tune was to ride it until it was time for a rebuild and then do the top and bottom. I mentioned this to my tuner and he asked why the bottom? I started talking about all the internet discussions and basically told him that being that it’s such a potential weak link that I might as well build up the whole motor for piece of mind.
He surprised me with his response... He feels the crank issues are over hyped and there is no reason that it should give out now if it hasn’t in the first 54k of somewhat aggressive riding. He actually said there’s folks building several top ends on top of the stock cranks. Even went as far as saying going 200k - 250k Miles wasn’t out of the question.
I’ve been convinced I should either do a full rebuild or a crate when my top lets go? Now I’m thinking a 107” with some head work might be alright and save me a butt load of cash.
So I go with the Internet masses and dump thousands on a crazy build or listen to the guy that just did an incredible tune and freshen up the top with a 107. Good thing is I have 3 or 4 years to figure it out.
He surprised me with his response... He feels the crank issues are over hyped and there is no reason that it should give out now if it hasn’t in the first 54k of somewhat aggressive riding. He actually said there’s folks building several top ends on top of the stock cranks. Even went as far as saying going 200k - 250k Miles wasn’t out of the question.
I’ve been convinced I should either do a full rebuild or a crate when my top lets go? Now I’m thinking a 107” with some head work might be alright and save me a butt load of cash.
So I go with the Internet masses and dump thousands on a crazy build or listen to the guy that just did an incredible tune and freshen up the top with a 107. Good thing is I have 3 or 4 years to figure it out.
Grand HDF Member
Joined: May 2010
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From: SWMO
The first time I measured crank run out on my 11' 103 it was around 10K mi. and fairly stock it was .007" Then came some cams and headwork etc. dyno said 109/116. I measured again after about 20K mi. of that and it was at .0085". I don't know how long it will go, but I wish now I had sent it off to Darkhorse in the beginning.
Issue is you just never know if and when. And if it shifts badly enough it can get ugly with other things which gets more expensive.
Issue is you just never know if and when. And if it shifts badly enough it can get ugly with other things which gets more expensive.
Thread Starter
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Outstanding HDF Member
Joined: May 2012
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From: Brentwood
The first time I measured crank run out on my 11' 103 it was around 10K mi. and fairly stock it was .007" Then came some cams and headwork etc. dyno said 109/116. I measured again after about 20K mi. of that and it was at .0085". I don't know how long it will go, but I wish now I had sent it off to Darkhorse in the beginning.
Issue is you just never know if and when. And if it shifts badly enough it can get ugly with other things which gets more expensive.
Issue is you just never know if and when. And if it shifts badly enough it can get ugly with other things which gets more expensive.
Stellar HDF Member
Joined: Sep 2011
Posts: 2,372
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From: NW Kentucky
I've been considering one of Fuel Moto's kits this next winter and questioning the bottom end. Their standard 107 kit seems to be about what I want for now. I'd like to go 110 but know funds won't allow it. The numbers for the 107 with stock heads are pretty impressive. Bike only has 3100 miles on it now so keeping fingers crossed that the runout is minimal if and when I decide to do this.
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Outstanding HDF Member
Joined: May 2012
Posts: 2,385
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From: Brentwood
I've been considering one of Fuel Moto's kits this next winter and questioning the bottom end. Their standard 107 kit seems to be about what I want for now. I'd like to go 110 but know funds won't allow it. The numbers for the 107 with stock heads are pretty impressive. Bike only has 3100 miles on it now so keeping fingers crossed that the runout is minimal if and when I decide to do this.
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
Time to take a deep breath, count to ten, then think of something else to think about! Sounds as if you are thinking several years ahead, so defer a decision for now and enjoy that 'new' ride of yours! Anyway, it doesn't cost so much to do a 124".....
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Ultimate HDF Member
Joined: Jun 2009
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From: OH
I was told the same thing at the builder that did my 107. They said that they haven't seen them shift as much as people claim. I have about 10k or more on my 107 at 126tq/116hp. We ride 2 up a lot and I don't baby it. All good so far. I would go for it with a good 107. The 96" motor is a turd. I had 2 of them. The 48H that you are running is a huge improvement over stock but the 107 if done correctly is fun as hell to ride.
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Thread Starter
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Outstanding HDF Member
Joined: May 2012
Posts: 2,385
Likes: 1,442
From: Brentwood
I was told the same thing at the builder that did my 107. They said that they haven't seen them shift as much as people claim. I have about 10k or more on my 107 at 126tq/116hp. We ride 2 up a lot and I don't baby it. All good so far. I would go for it with a good 107. The 96" motor is a turd. I had 2 of them. The 48H that you are running is a huge improvement over stock but the 107 if done correctly is fun as hell to ride.
78/62 Stock to 108/96 Fun
Grand HDF Member
Joined: Jan 2008
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From: Raleigh NC
at 54k I wouldn't worry about my bottom end either....probably wouldn't @ 100K either, if the bike is running with no issues.....
but, remember it's an engine, and even the bottom end wears out, sooner or later...
@ 140K I discovered a fingernail sized sliver of aluminum at my oil filter... not knowing the path it took, I opted for a full rebuild
but it made sence to me, to do the whole bloody thing, and ride for another 140k or better
but, remember it's an engine, and even the bottom end wears out, sooner or later...
@ 140K I discovered a fingernail sized sliver of aluminum at my oil filter... not knowing the path it took, I opted for a full rebuild
but it made sence to me, to do the whole bloody thing, and ride for another 140k or better