AP Custom and Precision LLC

AP Custom and Precision LLC Powersports service from tuneups, machining, engine rebuilding and performance parts

Beginning with a hand-me-down snowmobile, the passion for motor-sports industry was born. Continuing through several self-owned performance build and years of excellent mentoring, life brought me to Wisconsin where AP Custom and Precision LLC was founded.

947/951 build time! First engine passed pressure test at 10lbs for 10+ minutes with no leakdown. Specs on completed bui...
07/16/2026

947/951 build time! First engine passed pressure test at 10lbs for 10+ minutes with no leakdown.

Specs on completed build:
Rebuilt crank, .25mm WSM pistons, 6 hole base gasket.

Specs for second engine (in process):
New WSM crankshaft. 0.5mm WSM platinum series pistons, 6 hole base gasket, and the head was milled to tighten squish (fix SBT massive squish due to them recutting the dome) and increase compression over stock. I need to check final squish and compression numbers after assembly is finished.

Seadoo 717 crank seal and main bearing failure. Customer self-installed a new top end and very quickly identified that...
07/03/2026

Seadoo 717 crank seal and main bearing failure. Customer self-installed a new top end and very quickly identified that the crank was making noise. We advised them to not run it. Thankfully no damage was done to the top end and we were able to properly rebuild the engine for them! This is yet another reason it’s good to pull the crank on a 30 year old ski even if you think “it just needs a top end”

07/03/2026

Seadoo 717 crankshaft main bearing failure. Crank was making noise and sucking air by the mag side seal. Installing a new top end did not fix this issue and thankfully the customer didn’t run it after they heard the noise.

Saving PWC engines one cylinder at a time…. Or three… or by big batches. If your engine is low on compression, it’s tim...
07/03/2026

Saving PWC engines one cylinder at a time…. Or three… or by big batches. If your engine is low on compression, it’s time for a rebuild and we want to be the partner you work with!

When people say or post that they are jus going to “give it a quick hone and put rings in it” this is why I cringe! Wh...
06/23/2026

When people say or post that they are jus going to “give it a quick hone and put rings in it” this is why I cringe! When you are rebuilding an engine, the cylinder and piston are one of the most critical steps. This Seadoo 720 cylinder came in as a standard size piston that had some hone marks in it. Thankfully it wasn’t run the way it was because, while it looked smooth, had extreme egging and out of round that required it to be bored from standard to +1mm (.040”)! 😳😳😳 It wasn’t until the .003” finish cut prior to chamfering and honing that the last few spots were removed.

If you are looking to rebuild your engine you can send your cylinder in to us for inspection and we will look at it for free! If it needs anything we will advise you what if any work it needs and will supply the right parts to have it done right! The process is easy - just visit our website and follow the instructions at www.getapcustom.com/shipping and the linked work order form.

If you have never rebuilt your engine before and need some how-to help, check Nick’s videos on Today We Wrench

Update on the cylinders sent in for evaluation. The piston to wall clearances were .0012” and .0039”. This is much l...
05/23/2026

Update on the cylinders sent in for evaluation. The piston to wall clearances were .0012” and .0039”. This is much less than the customer requested spec of .0060”. After chamfering the ports, we got them honed to the desired clearances. If they had been run as they were they would have seized and ruined a brand new set of Wossner pistons.

As the old saying goes: “you can have it done fast, right, or cheap….. pick two”

A customer recently sent me a set of cylinders and asked us to check out the work their local shop had done because the ...
05/22/2026

A customer recently sent me a set of cylinders and asked us to check out the work their local shop had done because the shop mentioned they don’t measure the piston to bore clearance. Aside from that major element, we found the ports have zero chamfer on them.

Both of these are critical elements in a Seadoo engine surviving. Please make sure if you are having work done that you are using a reputable shop that is familiar with two strokes. If you are ever concerned about something, we are wiling to give a second opinion.

Available soon: Bigbore billet block with Able Performance head for a Yamaha 701. This setup would be amazing for yo...
05/22/2026

Available soon: Bigbore billet block with Able Performance head for a Yamaha 701. This setup would be amazing for your next build!

- Billet CNC block with amazing porting
- Wossner pistons
- Able Performance girdled style cylinder head with pump gas domes

This kit should be ready in a few days after the sleeves are installed and machining work is all completed.

This is a recent Seadoo 717 (720) engine rebuild for Sport Spec racing in Great Lakes Watercross Group. Excited to see...
03/13/2026

This is a recent Seadoo 717 (720) engine rebuild for Sport Spec racing in Great Lakes Watercross Group. Excited to see another engine on the line!

This week we got caught up on rebuilding some Polaris 350L 400L 400 crankshafts commonly found in Scrambler Big Boss and...
01/25/2026

This week we got caught up on rebuilding some Polaris 350L 400L 400 crankshafts commonly found in Scrambler Big Boss and other 90’s Polaris atv’s. These were set with new WSM connecting rod kits and All Balls man bearings. We true our cranks to ensure long term reliability.

If you need engine parts rebuilt or refurbished contact us today or fill out a work order form at https://www.getapcustom.com/work-order-form

Address

Long Road
Stockbridge, WI
54129

Telephone

+19204390938

Website

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