MS440 Build w/ thick 17mm crank balanced to 56% HD Spring, HD Pin. HD Pin? Whats that?

MS440 - 50mm bore x 38mm stroke
Thick 17mm crank (normal thickness is 15.5mm) balanced to 56%
HD Spring
HD Pin
(blaming @ImpulseRocket for this one)I did this on the 49mm 72cc "100notcc" due to this being the cheapest engine only listing. Around the same price range are 66cc in REALLY bad shape, such as thick black paint everywhere. I was able to adjust the timing on the 49mm cylinder, modified the stock head and sold it. I only needed the case and the other goodies, even though I have boxes of parts, it was either pay $76 for an engine only listing, or pay around $40 on a case only from CDH. There is a $25-$30 listing for just the case, it even says "8mm" however everyone receives 6mm cases.

Decking the case was the longest process by far. I put the piston at TDC and had roughly 2.5mm of the skirt in the intake port. I then took the piston to BDC and about 2.5mm was open from the top of the piston crown to the top of the intake port (cross talk) I decked the case to 2.2mm and filled the M8 crank case stud holes with aluminum 6061 hex bolts, cut the excess off so it is flush with the case, then put JB weld in (must use aluminum and no other metal) It made zero sense to add JB Weld first then to deck the case. It would be a complete waste on top of JB weld absolutely RUINS sandpaper. I took marker and drew strokes over the deck opening. The purpose of this is so when you sand it, you can see if you have high spots or low spots. If you're sanding it and there is a section where the marker is being removed but the rest of the deck is covered in marker, then you know that section is a high spot.

I bought the cheapest 1.5mm solder to measure squish. Using Fel-Pro 3025 (1.6mm) and the squish was so high that the piston crown wasn't biting the solder. I then made a base gasket out of Fel-Pro 3046 (0.8mm) and my squish was around 0.85mm which is perfect.

I need to make a very important note. When you drill the case to make new tapped holes to mount the saw cylinder, you MUST stick with whatever you're going to use as a base gasket. I made a gasket out of Fel-Pro 3025 (1.6mm) and it was so thick that each case halve couldn't "lock" into each other. I went down to 3046 (0.8mm) and it was perfect. I drilled my holes and tapped them. If six months from now, I decide I want to use gasket maker, I will run into issues because that would bring the case halves closer into each other, and as a result where my holes are won't align with the cylinder. I must stick with 1/16 aka 0.8mm thick gasket material for life.

HD Spring is this one here which is rated for 474lbs. Keep in mind, once you bore out the spring, shave material off etc, you do lower the max load. Stock spring is 275lbs or so, and the HD BBR one is 375 I think. I had a machinist bore it out as the "cups" on each end are 20mm OD. Do not shorten it, whatever you do. The OD was slightly larger than what the case was meant for and rubbed slightly. As opposed to shaving off material inside (the clutch bearings rely on the taper to be seated) so I took an M14 x 1.00 nut, put it on the shaft and spun my drill on the lowest setting. It shaved off the material where it was rubbing, so I went back in the case and shaved only where the rubbing was and where it needed to be shaved, instead of just shaving everything.

Now, @ImpulseRocket brought up a good point that I didn't consider. All these HD spring upgrades, but people forget that the parts on the shaft (the pin which is honestly the heartbeat of the shaft) isn't designed for that strong of a spring. I bought some super strong steel rod, and cut it down to 4mm x 20mm and made an HD pin. The pin in the stock clutch assembly is 3.7mm and literally would fall out of the threaded cup. This is a recipe for that pin to bend slowly overtime until it looks like a broken arm.

Lastly, I went with studs instead of the typical socket cap screws. I did not feel comfortable especially during the "testing phase" loosening and tightening black oxide steel hardware in super cheap chineseium. I did read it is ideal to actually drill and helicoil the hole so that your hardware is tightened against steel (stainless) as opposed aluminum. I red threadlocked the studs and bought M5 coupling nuts as it is easier to thread those on as opposed standard hex nuts.

Any questions?

1.65" CNC Mount was needed. I wasn't able to fit my exhaust in there. I was really shocked at the result, I now have more than enough room
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Just flexing having a thick 17mm crank. I had a 17mm - ZL-40mm and it was my best preforming china doll, most likely due to increased compression.

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Thick cranks Runwell thin.png

Transfers 1.jpg


This is the HD Pin I was referring to
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I widened the face of the port and not the port itself as I didn't want to affect timing. If I didn't remove material from the face of the port, then the port would block my intake manifold.

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440 front.jpg

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Now, @ImpulseRocket brought up a good point that I didn't consider. All these HD spring upgrades, but people forget that the parts on the shaft (the pin which is honestly the heartbeat of the shaft) isn't designed for that strong of a spring. I bought some super strong steel rod, and cut it down to 4mm x 20mm and made an HD pin. The pin in the stock clutch assembly is 3.7mm and literally would fall out of the threaded cup. This is a recipe for that pin to bend slowly overtime until it looks like a broken arm.
He was just mentioning that you had brought up the pin might not hold up to the heavier spring. He's not blaming you for anything, he's just explaining why he did this particular mod 🤣 (if this is one of your jokes, it's too early for me to comprehend.)
 
He was just mentioning that you had brought up the pin might not hold up to the heavier spring. He's not blaming you for anything, he's just explaining why he did this particular mod 🤣 (if this is one of your jokes, it's too early for me to comprehend.)
Just my dry sense of humor, not really a joke. He said I was to blame ;)
 
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