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KX450F Red Pipe

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Hey Gang,

This will be a little lengthy however any advice would be greatly appreciated. Just broke away from two stroke and purchased a single owner 2011 KX450f. Hour meter states 39 hours hopefully its accurate. Previously he raced novice a couple of seasons. Runs 1/2 race fuel and 1/2 93, Rottela T gear oil, no engine mods to the bike other than loud Mouth Intake and stock pipe. Owner stated set up with factory mapping.

Im here in the North East and as everyone knows its like the Arctic here. On the first viewing the bike was tough to start as it was a weekend of sub zero temp. After about ten kicks bike started and idled great. No smoke sounded nice and smooth. A week later I purchased the bike. Started and sounded great.

 

I've had the bike for a week now and I try to start every coupe of days. This weekend I started the bike with choke let it idle for a minute and the exhaust bright red, shut the choke and then shut the bike down, waited about 5 minutes and took the bike for a short ride up the road a seemed fine, once again the temps here have been consistently in the teens to zero. Also earned only use choke to start and don't leave it running on choke. After about three days I started it again, with choke on, shut the choke after 10 seconds and noticed the exhaust sight start to glow. Shut the bike down. Should the exhaust get that hot that quick?

 

During these start ups the cylinder is only warm to the touch even when the exhaust was glowing. I'm an above novice rider, ride aggressive woods and intermediate track.

 

Any advice on what I should be running for fuel, gear oil and antifreeze as well as any preventative maintenance checks I should check ASAP would be greatly appreciated.

 

Thanks in advance,

 

 

 

 

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I live in Michigan and run premium pump fuel,engine ice and Rotella t,all good stuff. The header is normal.

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Thanks Troy, wonder if the race fuel is necessary, owner claimed the lead helped lib the engine and fight off ethanol issue. Love the bike, it's a demon.

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Not necessary to run race fuel,no ethanol premium is good

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Thanks for the input, I'd hate to keep torturing the original owner however does anyone feel switching to just a good quality high octane and eliminating the 50% race fuel will effect performance? And is ethanol and issue with these 4 strokes?

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Do you know what compression the piston is? I would find that out before switching fuels... I would also check the valve clearance, that could be causing the hard start issue.

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Baileygunns, the bike has its original piston and rings with 39 hours, I'll try to find out compression. The owner mentioned he was running the race fuel with lead in it to help lubricate the engine and prolong life.

I was under the impression the tough start was due to the very cold temps, If I put a small office heater against the bike, for 15 minute or so she starts right up.

Thanks

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Baileygunns, the bike has its original piston and rings with 39 hours, I'll try to find out compression. The owner mentioned he was running the race fuel with lead in it to help lubricate the engine and prolong life.

I was under the impression the tough start was due to the very cold temps, If I put a small office heater against the bike, for 15 minute or so she starts right up.

Thanks

The "lubrication" properties were only relivant way back in the day before there were hardens valve seats, the exhaust valves would wear along with the seats. Today the valve seats are stupid hard. when was the last time you had to replace an exhaust valve because of face wear?

The only way I would consider it for lubrication was if I were running c630 seats. And even then I wouldn't worry much about it.

The main purpose for leaded fuel now is to raise octane. The only way to achieve 100+ octane is to add TEL.

I would recommend you run your bike with straight 93 or a race fuel equivalent octane. If there is detonation it will sound like a bag of marbles.

I have been able to run pump 93 on a 13.6:1 comp 250f in the winter without detonation. In the summer it would start to detonate so a race fuel was needed.

Running more octane than required robs power.

Edited by charper

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It is pretty normal for a header to start glowing where it connects to the cylinder when it is just sitting still idleing for a few minutes. The exhaust ports are fairly short so most of the heat from each combustion event gets transferred straight into the header. Thin wall tubing and an idle speed of around 1800 rpms and it doesn't take long to glow.

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It is pretty normal for a header to start glowing where it connects to the cylinder when it is just sitting still idleing for a few minutes. The exhaust ports are fairly short so most of the heat from each combustion event gets transferred straight into the header. Thin wall tubing and an idle speed of around 1800 rpms and it doesn't take long to glow.

I run my idle around 2400 rpm.

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It is perfectly normal for the header to glow. The titanium header is very thin to reduce weight and will glow red hot in 15 seconds sitting still. a stainless header will glow red hot as well. Start it outside at night and it really lights up.

Use to light smokes off my exhaust when my lighter got wet.

Ditch the race gas and run straight 93. Many stations now offer ethanol free fuel

Edited by Grabbing-Gas

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