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After Market Popup Piston & Cylinder kits

qurotro

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The exhaust port on the Hyway 288 is over 3mm bigger than it is on the K&S cylinder I have. The intake is a little over 1mm bigger.
Hm.. My 288 runs Hyway jug too. From what i remember it's quite identical from the oem and chamfer a little more than oem on ports. But the squish is like 0.04" without gasket though.
 

Ronie

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Was your oem jug a K&S or a Mahle?
 

Wonkydonkey

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Iirc, my hyway bb for the 660. Does not Freeport, no gasket and a squish of around 20thou. I can’t remember exactly what it was but I needed to not use the gasket.

The transfers were a little out of even.and it ran like a dog compared to the last bigbore I had which did Freeport and drink fuel. But I toasted it.. and sadly I tossed it before I got any other details from it..

Yes I’ve been wanting to get a pop up piston but...... I’ve been waiting till hopefully they are a bit cheaper here in the uk, also I’ve got tomany other projects on the to do list..

like I need make my ms211 better than it is... someone on here posted a vid of there’s and it really chewed through wood...
 

Kiwioilboiler

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I've been messing with the Hyway popup pistons, I've got 2, 350 huskys up into the 180's comp with base machineing also, my stock 350 is at 115 comp.
A few days ago I put a Hyway popup in my 357 Husky wich already had a base gasket delete, a muff mod and the main jet cross drilled in the zama.
It was blowing 177 on the comp gauge. After some porting & the popup piston install, and after two tanks of fuel she's making 198 lbs. comp.
How have these stood up long term OldGuy? I have a 351 on the way that I'm unsure how to progress. A 45mm closed cleaned up OEM cylinder and hyway popup might be a way to make a strong (for a 50) torquey work saw I feel.
Edit: saw turned up and is a 353! So cylinder part secured already.
 
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BonScott46

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Any feedback from guys that have been putting a lot of hours on these pistons? How are they holding up?
 

president

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The dome is usually higher than an oem piston crown as opposed to us making our own on a lathe and dropping the cylinder over it.

One can weld a popup to a crown and turn it down as well, but a manufacturer has the ability to have their slugs cast and machined any way they want them.

BTW, the reason the BB 660 kits free port so badly is that they have shorter skirts than oem. That’s done to insure they fit the case they are put on. The factory 54mm slug’s skirts dip below the case pad at BDC. Usually there is not enough side clearance to allow the 56mm slug to drop down into the case, so the AM responded by removing the skirt. That’s why the Freeport so badly, it’s not the jug design, it’s the intentionally short skirt.
I tought (Harley) would chime in about his preference for short skirts)?
 

Ketchup

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I’ve been milling with a 395 Highway BB Popup for over a year. No problems so far. I’ve installed several 200t Highway Popups. All still out there without a complaint. Most people say the saws have more power.

I installed several 372 Highway BB poppers as well. The displacement is noticeable, though not all of them hit the RPM I want. One threw a circlip after about a week of use. Could have been my fault, but I don’t trust the Highway clips anymore. Another one died at about 2 years. The guy never brought it to me after that so who knows what happened? At least three are still in tree trucks doing their job.

Edit:
All three of the Highway 395 BB popup kits I have measured have had a squish of 0.040”.

I have received several Highway kits that I sent back because the port castings were messed up. The pistons have always been fine.
 
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TX_Welder

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For those that have welded and machined popups, do you shave some weight off the piston elsewhere to make up for what was added to the top of the piston ?

A mechanic I used to work with told me you can always go lighter on a crank but you never wanted to add weight to the rotating assembly. In my experience this has been the case.

Is there any noticeable vibration increase with a pop-up?
 
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