This is about what we are seeing on regional and national level engines. I know of many engines that have gone much longer though. If peak performance isn’t your main concern, you can definitely get away with much longer intervals before rebuild. I know a few guys who got the engines in back in 2017 and pounded almost 50 hours on them to durability test them and there were no failures. Sure, small loss of performance after that much running, but no catastrophic failures.
I’ll add to this data point here. Chris and I have 3 KA’s from 3 “National” builders (comet / Woltjer / BBS). All recommend somewhere between 8-12 hours if you are competitive and run at the front. All recollect every 3rd-Ish top end to bottom end ratio.
We have BOTH had premature failures in the 8-10 hour range, we have also BOTH won races with motes with around 12 hours on them.
Personally I feel like 12 hours is about that happy spot on the top ends, but you can certainly go longer if you are just interested in racing and not in the mix for wins.
Any of these recommendations are just that. The thing starts to feel flat find 10 hours just send it for service.
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Thanks.
On the KT100 we would start seeing hairline fractures on the cases at the main bearing pockets around the 4-5th bottom rebuild. I wondered if the KA100 was the same. Given a KA100 is 4-5 times the money of a KT100 I could see individuals running the cases longer to save on buy a complete new motor.
I’d also add that reliability is important for their reputation too.
It’s interesting to see the difference in experiences here with longevity. Makes we wish we had a better way of measuring wear/load than simply time. I like fuel a little more as a measure, but even then that doesn’t quite tell the full story of what the engine has endured.
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While the retail price appears higher than a KT100 in reality when you factor in a clutch, header and pipe and the work required to make a KT competitive the KA is about the same money if not less. Also, and I am sure this will change in time, the KA holds value well.
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Sorry for the late response, but what is your opinion on your BBS engine, considering buying an engine built by them.
I have four BBS KA engines. Two that were box stock and sent to them for blueprint at first rebuild, and two that I bought new already blueprinted from them.
All of the motors are strong and have run flawlessly, but the biggest thing is Brian’s willingness to just help and answer questions. I only race at a club level but he has always responded to my questions as if I was somebody. With that said, I can’t recommend them enough. Just great folks to deal with.
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what’s the cost of a typical top end rebuild if I was to send mine in? i’ve been looking but i’ve seen. anywhere from $250-800
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I can’t say enough good things about Brian and particularly his customer service in a field where that’s often a secondary “product” for these engine shops.
Cost will depend on who you use and how much “extra” you want. Parts are just over $500, and I use P1 Engines, and pay around $500 for Labor, Break-in, and Dyno, so a little more than $1,000. But along with that, I can text/call/email Jesus at any time and typically get a quick response for help.
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$500 must include a rod kit. There’s no way a KA piston kit is that pricey. Would make sense regarding the labor figure at that point too.
The rod alone is $400 so prob not included at the $1k rebuild price. Rods seem to be items to inspect and only replace if there are signs of issues. My last rebuild on one of my motors the builder split the crank and inspected everything but chose to continue with the same rod and simply replaced upper and lower rod bearings not the rod itself.
Top ends in my experience are $600-800 with dyno/ break-in.
The more major service I just mentioned with splitting the crank, replacing rod bearings and a more in-depth bottom end was $1100. Add a rod to that and you’d be around $1500.
Yikes, I was off base…but even looking at the USA retail price list the parts for a top end are still only $250 included gaskets and o-ring. @Zebug is P1 charging above retail for parts?
The cost to maintain a single-speed race engine still blows my mind, and is the reason a switched to shifters back in 2010. Granted that was in the Stock Honda heyday, but even a Rok Shifter piston kit + cage bearing is $155 from PSL today. Switch to shifters. You know you want to 
oh wow. so a bottom end is only $1100 compared to about $700 for a top end. would it be more cost effective to just buy a new engine about 15 hours after your first top end? because then you would probably need a top end and a bottom end which would run about $2,000 and a new engine is just $1,000 more.
For just a top end? I’ve had 3 different builders for my KA’s and they’ve only charged $600 at most for a top end including dyno. $1000 should be a full rebuild
What’s the purpose of the dyno? Just a verification of the power or does it include engine break in?
Power depends on the carb setting & exhaust… I’m just wandering
Little bit of both. Dyno will include a break in, you can’t dyno a motor that hasn’t been broken in, and it also gives updated info on things like powerband. Sometimes after a rebuild the engine gets a little stronger or makes some power in a different area rev range, so having a relatively updated dyno sheet is always convenient.
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I guess it depends on what parts alone are being changed. All prices I am charged is retail, but typically more is replaced than just the piston. The reeds get changed, carb rebuilt, and it actually looks like the last time had the main bearings and seals replaced as well. The time before would have been $700 for the top end. I just didn’t look at the full itemized list because I sent it for the top end, but since he does a full inspection, he felt there were more to replace.
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That $700 sounds more reasonable. I usually just send in the motor and say “Do what you need to do and let me know what you did when you’re done.”
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Do we have list of engine builders per state? I’m looking for one in Florida.
AM Engines is in Miami. Anyone have dealt with them?