Motor life expectancy...

Cesar Rull · Posted: Mon Sep 24, 2012 8:11 pm Post subject: Motor life expectancy...

So I am really baffled by the information below.

I got this via e-mail from a friendly retailer regarding the life of the motors for karts:

"Rebuild times for the average Honda CR125 'stock moto' is 50-60 hours between complete rebuilds. ICCs tend to be between 20-30hrs."

So this sound to me like these motors are very expensive and don't last very long !!! What am I missing here?

A Honda CR125 is a bike engine, how can it need a rebuild after 50-60 hours? what contributes to this? - People don't rebuild their bike engines that often do they?

Along those lines, What is the typical going rate to rebuild a Honda versus and ICC. Are we talking about 1000.00+ dollars every 3 months if you drive every weekend?

Please help me understand how this works? It seems like a 4K investment on a motor only for a few short months...

Charles Kaneb · Posted: Mon Sep 24, 2012 9:22 pm Post subject:

A long weekend of karting's about 6 hours of runtime. That's with practices and races on both days.
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Jim McMahon · Posted: Tue Sep 25, 2012 4:41 am Post subject:

To be honest those figures are on the high side IMO. I don't think I'd run a moto for 50hrs without looking at it and expect something not to break, but they did say full rebuilds so you would figure putting a piston in there at the halfway point. As far as the CR goes, sure it was made as a bike engine originally, but when its used on a kart its gets a harder workout than it would ever see on a motocross track. Way higher and sustained RPMs, much longer time on full throttle and a more aggressive pipe that makes more power.

It might seem like a lot of money at the outset, but if you consider the speed then its great value.

How much track time/testing have you budgeted for? ie fees, transport fuel etc..
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Cesar Rull · Posted: Tue Sep 25, 2012 5:11 am Post subject:

well being new its really not a question of much money I have budgeted for but rather how much does a rebuild cost?

I guess the question is, is it hard to rebuild any of these motors? or is it a matter or opening them up and just changing some parts like you would on the motor of an RC car? (get a new piston, new bearing and sleeve)

In such case there is a fun factor in doing that and you also save some money. Because if I have to pay whatever it cost someone Ill go broke !!

So tell me guys, how much does a rebuilt cost average if I pay someone versus if I do it? (assuming a person can do it without the need for any special tools other than a bearing puller of some sort).

Jim McMahon · Posted: Tue Sep 25, 2012 5:58 am Post subject:

Well on that end of things motos are handier to DIY rebuild because you can just buy a complete crank and swap it out. The KZ/ICC cranks are rebuild-able so you usually press out the crankpin, replace the bearing press in a new pin then balance it bit so quite a bit more more skill and experience required.

Other than that, both of the motor types are pretty straightforward mechanically. A little bit of knowledge with the transmission will help. Top ends\pistons are pretty easy and those you could certainly do yourself.
Again it really depends on your budget, once you figure that out you can slot in what you think you can afford for rebuild and so on. Typically I would say a piston or two a year and a full a the end of the year but it depends on how much driving you think you can afford to do. I know this is a kinda moving target but I guess you could start off by saying $1000 for the year in motor parts. A full rebuild is about $700 ish so that's giving you some room for a couple of new pistons/rings/reeds and some stuff that might break.

Full CR rebuild cost from extreme: http://www.extremegokarts.com/cr-125-stock-moto-engine-rebuild-p-207.html
Here's a guide for rebuilding a CR125 if you wanna DIY it: http://metal-matrix.com/cr125-rebuild/
Guide on rebuilding a KZ/ICC: http://www.greenflagkarting.com/gfk_products/tut_intro.php
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Greg Wright · Posted: Tue Sep 25, 2012 6:04 am Post subject:

Most folks over estimate the amount of time that they put on an engine during a race day. In most cases you won't put an hour per day on the engine. You might be there 8-10 hours but you are only on the track for a few 10-15 minute bursts.
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Cesar Rull · Posted: Tue Sep 25, 2012 6:45 am Post subject:

@Greg, that is right. After driving for 12 minutes most people usually want to take a break. And from what I hear track limit the amount of time you can run (session).

@Jim, thank you for the links. I was right, the top end is pretty easy to do, and just did a quick search on the piston kits and they are about 100 dollars.

I can afford that every 3 months...

However when people say the bottom end, it mainly means a transmission rebuild? - that seems pretty doable. A bit more complex but I am sure once you start to do it and follow the DIY its not that bad. However the rebuild seems a bit more pricey. But again if I have to do the bottom every 12 mo. Its not really that bad. Am I on the right track?

Again just to get my terminology straight.
Top end = piston replacement / cylinder look over etc.
Bottom = transmission, gears etc.

Benn Herr · Joined: 18 Jul 2001 Posts: 1580

By "Bottom End" they don't mean transmission parts. It's usually a crankshaft/rod assembly and main bearings and seals. It's unusual for any transmission problems to happen on a Honda or an ICC/KZ.
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Jim McMahon · Posted: Tue Sep 25, 2012 7:06 am Post subject:

Transmission really needs very little work unless abused/run dry. Inspect and or replace clutch plates maybe. Bottom end usually means main crank bearings and bottom rod bearing at least and tends to be more expensive as its more labor intensive. Throwing a couple of new bearings at the tranny wont do at harm.
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Cesar Rull · Posted: Tue Sep 25, 2012 7:54 am Post subject:

So then, I am gathering that doing a rebuild is really not that big of a deal.. unless you need to get a new cyclinger (which is 400 bucks). If you can do the top end rebuild then you looking at about 100 dollars and a few hours of your time every couple of months. (Depending on how often the karts is raced)

The bottom end rebuild being only bearings it just sounds more time consuming that 600 dollar fee for a complete rebuild, the largest part of that fee is labor. Do you guys agree ?

Jim McMahon · Posted: Tue Sep 25, 2012 9:51 am Post subject:

You are on the right track, a piston or two during the year and a full at the end, if you have put enough time on it.
The full rebuild I'd say is about 50/50 labor and parts, it includes a complete crank which usually includes a new rod but check with them to be sure.
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Cesar Rull · Posted: Tue Sep 25, 2012 11:23 am Post subject:

Thank you. I just called the friendly retailer who game the above (OP) information. I am very please to learn many things related to the intervals of service and use.

I was told that 50-60 hours for an average user like me could mean 1 year. before a full rebuild or even a top end refresh. It all depends on how lean and much I run my motor.

The question now is.. what motor to run. Honda/ICC.
It was also mentioned to me that a Rotax was pretty similar in longevity to a Stock Honda. Unfortunately, the only Rotax shifter is a DD2 and I have already committed to a chassis.

Tom Barth · Posted: Tue Sep 25, 2012 4:22 pm Post subject:

Cesar,

The choice is simple. If you have just spent money on a kart shifter chassis, then put a kart shifter engine on it. Wink

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Chris Reinhardt · Posted: Tue Sep 25, 2012 4:35 pm Post subject:

I agree...

CR
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Tyson Henry · Posted: Tue Sep 25, 2012 6:36 pm Post subject:

50-60 hours for a top end rebuild? I dont think so.