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Ugh. I guess is going to get complicated after all.
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orwell84 wrote:
Ugh. I guess is going to get complicated after all.
Easy peasy, you can knock that out. Going to pull my jug and tune my exhaust port too before I run it.
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BajaRob wrote:
Easy peasy, you can knock that out. Going to pull my jug and tune my exhaust port too before I run it.
I don't understand the where/how/why of welding the crank pin.
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orwell84 wrote:
Ugh. I guess is going to get complicated after all.
You can definitely just stick the cylinder on and aim for 1.3mm squish. But it's free power to be honest with the port width and adjusting the port timings. Even if you're building a tourer, it's worth doing.

And it's not going to do wheelies, or be a power monster, gearing will do that part. Just adjust the gearing characteristics to how you want to ride.
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orwell84 wrote:
I don't understand the where/how/why of welding the crank pin.
I thought mazzus were welded now…
Welded
Welded
Not welded…
Not welded…
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⚠️ Last edited by 108 on UTC; edited 1 time
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I do them like this, never had an issue. MMW was doing laser welding for SIP / Serie Pro cranks, don't know if there's a welded Mazzy…
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orwell84 wrote:
I don't understand the where/how/why of welding the crank pin.
😆 I ment tuning up the exhaust port. If you don't have a tig I would definitely have someone weld the crank pin for you.
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BajaRob wrote:
😆 I ment tuning up the exhaust port. If you don't have a tig I would definitely have someone weld the crank pin for you.
I am TIG-less. But I do know a guy. He welded up an absolute door stop of a 2 port case for me. Being a 2 port case, it's still kind of a door stop.


The crank pin looks fairly straightforward.

Exhaust port. Maybe. I will measure the timings and see what I get.

Ignition. Do I really need variable ignition? I have a new PX stator in the bike that I set up for full DC. After a lot of fussing and wiring repairs, it makes everything go. Battery was still charged after sitting all winter. And that's on a Stella.
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Still mulling over this crank and questioning if it's the best choice. Makes me realize again that you can't just throw off the shelf parts together and expect it all to work out.

Going to a reed valve brings up a number of considerations with the shape of the crank, namely reducing the volume the crank webs take up to make room for fuel or changing the shape to allow fuel to flow through. There is also the position of the crank which affects how much it restricts fuel flow.

I'm guessing that these changes vs a rotary crank have the potential to reduce the strength of the crank and make it more prone to twisting, as does increasing the stroke. And there we have the age old balancing act with performance vs reliability that crops up with every engine in the quest for power. And then we get to the solutions for the problems that result. Reading up more on welding the crank pin, it seems that it's somewhat controversial.

The crank I bought clearly doesn't have the pin welded. The only downsides I came across in looking at this solution was the potential to warp the crank when welding and that it makes the crank harder to separate down the road. I don't think these are big considerations with this crank and welding the pin is low cost insurance. A couple TIG spotwelds is not gonna warp the crank.

I'm hoping that the low level of tune I'm aiming for and my sedate riding style will make twisting the crank unlikely. In retrospect, I might have gone with a Malossi rotary case and chosen parts closer to stock. Probably overthinking this, but I like to have a basic understanding of what I'm putting together.

Thoughts?
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Don't know much about crank styles for for reeds but I would definitely weld that crank. SaFiS has tons of experience with all the scoots he has and works on to not take him up on that recommendation. I read lots of reports of the Mazzy cranks wandering in my research. You already have the crank so might as well use it. Like you said, not pulling wheelies or hauling a trailer with it.

I was on the fence about which cases I wanted too. Even though the SI style carb is an odd design for me, I picked the rotary case to keep it simple and more stock like. Definitely want a robust touring engine and something on the smoother running side. Hope the SIP crank I got gets it done. Was just going for a more plug and play gig like FMP did but from the reports I've heard Jack and 108 talk about, makes sense to get that exhaust port tuned better. I should have mapped my cylinder anyway. I was just being a lazy bastard. Haven't run mine yet so I'll pop it off and get it done.
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orwell84 wrote:
Still mulling over this crank and questioning if it's the best choice. Makes me realize again that you can't just throw off the shelf parts together and expect it all to work out.

Going to a reed valve brings up a number of considerations with the shape of the crank, namely reducing the volume the crank webs take up to make room for fuel or changing the shape to allow fuel to flow through. There is also the position of the crank which affects how much it restricts fuel flow.

I'm guessing that these changes vs a rotary crank have the potential to reduce the strength of the crank and make it more prone to twisting, as does increasing the stroke. And there we have the age old balancing act with performance vs reliability that crops up with every engine in the quest for power. And then we get to the solutions for the problems that result. Reading up more on welding the crank pin, it seems that it's somewhat controversial.

The crank I bought clearly doesn't have the pin welded. The only downsides I came across in looking at this solution was the potential to warp the crank when welding and that it makes the crank harder to separate down the road. I don't think these are big considerations with this crank and welding the pin is low cost insurance. A couple TIG spotwelds is not gonna warp the crank.

I'm hoping that the low level of tune I'm aiming for and my sedate riding style will make twisting the crank unlikely. In retrospect, I might have gone with a Malossi rotary case and chosen parts closer to stock. Probably overthinking this, but I like to have a basic understanding of what I'm putting together.

Thoughts?
First one of those cranks I've seen with SIP stamped on it. Got to be at least grade B now. The cranks only twist when they are part of a significant overheat. Don't overheat it, no problem.
Once its welded that's it. Very difficult to change the conrod in the future.
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Jack221 wrote:
Once its welded that's it. Very difficult to change the conrod in the future.
Which definitely is the downside to a welded crank
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whodatschrome wrote:
Which definitely is the downside to a welded crank
Right. There are always downsides and no guarantees. It's just expensive enough for a crank to not be disposable. But whatcha gonna do? If it pops, it pops.
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orwell84 wrote:
Still mulling over this crank and questioning if it's the best choice. Makes me realize again that you can't just throw off the shelf parts together and expect it all to work out.

Thoughts?
I have the same crank, has the SIP logo on it, I measured if it ran true straight out of the box, was pretty straight, not perfect, gauge needles moved but not enough to register a reading.

Installed it, ran it, but preferred a full circle crank for responsiveness off the line, I'm guessing inertia and crankcase pressure probably being a factor. Just me being anal, especially when i had to crack open the cases to change the gearbox at the time.

I've never welded a crank, if it comes already welded, thats great, added bonus. but if the crank twists its usually something thats happened, like a seize... I just run them as is and worry about longevity later... the worst case scenario is a crank swap, which on a p largeframe, I'm more than happy to do.
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