When is it time for a rebuild?

Out of curiosity, after how long should a world formula engines internals be checked out/rebuilt? My engine is 3 years old, with a total of about 21 race days. The timer broke so not sure how many hours. It’s been well maintained, new clutches and carbs whenever needed, oils been changed after every race, etc. it’s a sealed engine as well. Is it worth it to send it to a dealer for a rebuild and dyno?

I noticed you haven’t gotten a response. I asked this question of the LO206 motor and got this response:

206 “Rebuild” = head and carb. We call them “refreshes”. Yes, they are still legal afterwards.

If you have an issue with the short block, it can be replaced. They are about $300 MSRP (~$500 parts and labor through us).

We go about 10 hours before top end refreshes (~$175 parts and labor) and 2-3 seasons before even thinking about a short block.

Not sure how much this translates to the WF motor but it sounds like at the very least a top end is in order.


I’d say I’ve got over 10 hours. Carb only has about 3 hours as I replaced it so it should be fine.
Is this a realistic worry of mine? Would I gain pace if I got a rebuild? Or have I just hit a driving plateau and am trying to find excuses

I have no experience with 4 strokes but I would guess you might gain a little HP. Perhaps someone could do a compression test and that may show how much loss you have. It is fairly simple just need a compression tool that screws into your spark plug hole. If you have an engine builder in mind it might be worth asking them some of these questions.

I cant speak to the WF, specifically, but I would never go 21 race days on any 4 cycle “race” engine. Yes, you are definitely giving up power. At minimum you need the valves re-sealed.

We could get into leak down checks and maybe even compression checks, but realistically, you need to take it to someone you trust to get the thing checked up and back to peak performance.

WF engine tend to retire themselves vs LO206, I would check them every season in general. Since it is a sealed motor, like Robert said, the rebuild/refreshes is only limited to top end and carb. They usually check the valve, sand the head to flat if cupped and some other magic. It will bring the engine peak performance back for sure. As I have seen on 206, Dyno is pretty much useless.

Here in MN, WF on our track is not sealed, and we are running on a SKC spec, shimmed valve and no rev limiter.

Elias, just to give you some perspective my engine also has 3 seasons on it. We’re probably giving up some power but the results don’t lie. Obviously no engine is the same but I usually run them 2 seasons and just replace them. This year is going to be number 3 on this particular engine because I was planning on running shifter this year but you and Nick heckled me at the beginning of the season and I decided to try to win the championship again! :joy:

1 Like

ah shit. Course the guy who walks me on the long track has an old engine. I’ll see if DRT can seal it and if they think I should get it rebuilt. Arent you glad we heckled you? pretty close up top in WF. You wouldnt have as much fun just running laps in shifter.