Time to replace?

Brianf60

Member
I pulled the cylinder head off to have the valve seat ground and noticed this wear on the cylinder. Not very deep. What are your thoughts? Is it worth having the head done or should I just replace the engine. Also is this more for 1 valve guide to be protruding much further?
 

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What about the compression pressure? I always kept my snap-on gauge close by. I've been known to say "compression is the holy Grail". It would help to have some comparative readings from your friends. Any loss in compression is never good.
 
Im going with yes on the valve guides . Wait for confirmation or denial .
Can see some scratches on the cylinder , the tops not real clear .
No comparative result with either a compression test or leak down .
Makes it a opinion decision .
Visually its acceptable IMHO . Its not perfect .
Better air cleaner maintenance going forward .
Fix the head then test it . Or fix the head buy a short block or complete engine . Its a quandry
Jimbo or Brian will give honest ,trusted advice .
 
Ya no easy answer. I don’t have a compression tester or leak down gauge at the moment. I lost $80,000 in tools in a house fire last year. I guess it’s a good excuse to replace them. What’s an acceptable reading for compression on these and how many pulls? I assume we are looking and the reading on the first compression stroke and then the max? For what’s its worth I expect that refreshing the cylinder head will be close to the cost of new one in my area. I’m in Canada. Knowing the heads needs done there is no point in a short block. The cost of a block and rebuild or new head is about the same a brand new engine. If it’s not cost effective to fix I will just buy a new engine and lap the valves the on this and put it in the trailer as a spare. Next year my youngest will likely be ready to start driving and engine runs good enough for him to get in some seat time. Our performance did drop off through the year but I had written it off as driver/ confidence. My son was only 6 and really doesn’t give very good feed back. He had had a few crashes and was racing with kids the were older then him. I guess I should get some baseline numbers on the engine so I can better test it periodically. Lap times aren’t really the answer for us at this point. He isn’t consistent enough and the layout at our home track changes so often I don’t want to make discussions based solely on lap times.
Thanks for the feedback and keep it coming!
 
They say that cleaning up the seats is the ticket on these .
With what you described that would be the route i took , new valves lap them in or grind if possible .
Purchase a new engine .
 
Trouble is I’m in a Canada. The short block is $525. Complete motor is $825. When you ad the cost to freshen up the cylinder head I’m almost there. Sounds like complete engine is more economical. Plus leaves with 1 of everything for a spare if ever needed..
 
The valve guides are normal. The cylinder looks tired to me, but I would use a compression test (and a dyno test) as the main determination. I prefer a seasoned block over a new one and looks are not as important as performance.
 
Often times refreshing the head and having the valves and seats professionally done makes more power than a new engine.
The stress put on the head by the head bolts, the exhaust manifold, the spark plug etc and the countless heat and cool cycles will distort the valve seats. They won't be round and will have dips in them. You can lap the valves for a very long time and it won't straighten or true up the seats. Not to mention the grooves you will get int the valve face. To get them right they need to be machined.
I do them every day and have seen countless bad valve seats.
I will say that the valves and seats work very well when new. It takes a while for them to get out of shape.
Best of luck.
Jim
 
My suggestion would be to freshen the head regardless of the direction you go with a new engine.
The very best 206s to go across our dyno have been 20-25 race day bottom ends with a fresh valve job cylinder head (generally the first cut is the best.)

I just wrote an article for our Facebook page last week detailing valve and seat maintenance (several pictures too.)


With that much scoring in the cylinder, I suspect that your air filter maintenance needs an upgrade. If the wear is in the rotating assembly as much as we see in the cylinder, there may be an oil issue as well.

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
If you did not clean the piston, how long has it ran, what are the carb settings and what are you using for oil? The crown of the piston is extremely clean for an engine that has been raced. The edge of the piston looks pitted, and the top coloration of the cylinder is unusual.
 
If you did not clean the piston, how long has it ran, what are the carb settings and what are you using for oil? The crown of the piston is extremely clean for an engine that has been raced. The edge of the piston looks pitted, and the top coloration of the cylinder is unusual.


I caught that too -- wet weather racing I would assume. That tends to wear the cylinder prematurely also.
 
Thanks for the feedback gentleman. I think I will have the head done either way. If the kart is down on power (when the snow finally melts) I will have a fresh spare head for the new motor. No cleaning to the piston. I thought I was pretty good about air filter cleaning and oiling. We did some wet weather racing and practice later in year so that may have contributed to this. Should I be using one of the air filter guards for this? This motor does have a tons of hours on it. We got it slightly used and then my son put a ridiculous amount of hours on this practicing. It really owes us nothing at this point. I have always used Briggs oil (probably not changing as often as I should) and again we got it used with the kart so who knows what was used in its first life.
 
Here is a picture of cylinder head if that helps at all.
Thanks,
Brian
 

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If you ran in the wet (especially without a rain-guard) - it ingested some moisture.
If it sat for long after that, could explain the discoloration above the top ring in the cylinder.
 
I have a new un used head. Do you recommend getting the head checked before racing? Does seats need to be cut and true'd if new?

Thanks
 
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