This is the question swimming around in my head. I was talking to a friend today about Jamie's 107" kit and I was pretty much sold on it. My friend said he would be afraid that the cylinders wouldn't hold because that much bore makes them too thin. He said he thought he would go with the S&S. So, I came home and looked at the S&S webpage and sure enough, S&S cylinders are made with a different material and they do not even want the stock cylinders as a core. Their 106" cylinders, as I said, are made with a different material, which they also say is "much stronger" and that even with their stronger cylinders, that is as big as they feel safe boring. I thought I was sold on Jamie's 107" but after talking and reading more, Im questioning everything again. I like the Wood cams torque curve very much though. Here's why, I drew the dyno sheet on Jamie's website over the top of my dyno sheet with the 255 cams and the curves are essentially in the same place as far as left to right. The difference is they are higher up (more power). What Im saying is the power is in the same rpm band, there is just more of it. Now I dont know what the hell I'm gonna do. I'd be sick if I scissored my crank or grenaded my motor. Now Im wondering how the Wood tw555 cams would work with the stronger S&S jugs?

 

I am interested in hearing the comparison, too.



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When I built my motor, I was also torn between the 103" and 107". I ended up going 103" because I was also a little skeptical of a bore that large in stock cylinders. Had S&S had their 106" kit available I would have went that route.

That said, there are an awful lot of 98" and 107" motors running around with no problems.

Zach

 

Does Fuel Moto have a 98" BB for the 88" stockers? I wasn't aware of that.

 

You better do the crank if thats going in a heavier bike!!! What about axtell cylinders??

 

It would be in my RKC. Not exactly a light bike. I have not looked at axtell stuff but maybe I should consider that.

I dont mean to quote Jamie from Fuel Moto but I believe he said the crank is good for up to about 125 ft/lbs. TQ and thats a little higher than the dyno sheets I've seen with his 107" kit. Ive also seen where guys have asked about headwork to compliment his kit and Im paraphasing here but the answer was basically, The increase in gains with headwork would be substantial, however, strengthening the crank would be a wise idea if one wanted to achieve more power than the kit alone would give. Part of the reason Jamie's kit is so appealing is that you get the good gains in power without headwork. All the gain I would ever want as a matter of fact and in the rpm range I want since the Wood cams are the centerpiece of the kit. I have no reason not to believe him about that, or the cylinders he has with his 107" kit. He always seems to be readily available to help folks even though they are becoming a rather large company and I know that Bob Wood is highly respected in the cams world and I dont think either of them would endorse each other or package a kit with each others parts without the best of intentions. Sometimes its just hard to predict how good a part/parts/kit might be until it has been tested in the real world.

 

There are many companies making 107 kits & I haven't heard of anyone having problems with them. Axtell sells a 107 kit also & they use stock cylinders that are bored, not aftermarket cylinders. S&S is a highly reputable company & I think they were being safe with their 106 kit. It takes a very reputable machinist to properly bore the cylinders out to 107 specs, they have to be sure the bore is perfectly centered in the cylinders, not always the case with mass produced cylinders from HD. I personally would never go with HD BB cylinders since I know a good machinist is going to hold the boring tolerances to a much higher standard. I believe any good company that has experience with doing 107s is going to give you excellent results, there are just too many 107 kits out there to not have heard of problems if there were any. It usually only takes one person in 10,000 or more to hear of problems on this forum, so I wouldn't worry about a company with as good a reputation as Fuel Moto.

 

I agree with the above poster. I think S & S just "markets" their cylinders that way to keep people using theirs instead of going with someone else's 107". I''m going with Jamie's kit just because I love the work he's done on my bike so far and trust him to do the 107". If it weren't for that I'd have no problem going with the S & S kit either.

 

What is the actual piston size for the 107"?

 

Axtell lists it as 3.932 that's .057 over a 103. I know when HD first came out with 95" pistons for the TC88 they made them in .030 over, I had a friend that figured he might as well have a 96.5" for the same price, now they go to 98" & 107". There has to be thousands of them out there by now, I'm sure we'd have heard if there was any problems.