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borjawil

Help with CR480

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1983 CR480. New piston, rings, gasket set. Was told reed valve was new as well. It starts up easy from what ive been told about others.

heres my problem. It smoke quite a bit. starts right up with choke down but idles high. turned the idle screw out but no change. does rev. When choke is pulled up the idle lowers and bike dies after about 5-10 secs.

is the mix screw and air screw or fuel screw? I think its an airscrew. how many turns out should it be?

Also this is my first two stroke what oil should I used in engine and in the fuel? How much should i put in engine? Im planning on changing the oil soon.Would like this to be good to go by friday night, want to join some buddies at the dunes sat morning

Ive been told the crank seals one or both could be bad and causing it to smoke as well as the idle issue. Anyone has a manual they can scan and email me for changing the seals? or a online manual? or really good directions and pictures?

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Sounds rich on the idle/pilot circuit. Try 2 turns out on the air screw. Also try the following:

Good fuel such as 110 race or 100LL av gas mixed 40:1 with Maxima super M or 927 castor.

Clean and oil the air filter.

Make sure the float level is good in the carb (I don't know the spec, you will have to look it up).

If still rich, try 1 or 2 grooves higher on the needle clip.

If still rich, keep going out on the air screw. If past 2.5 turns, you need a smaller pilot. Look for a local shop that takes care of the vintage racers. I bet they will have the Keihin jets. If not, order from Sudco.

Hold the bike up straight and fill the oil slowly until the level is up to the threads on the fill hole.

My clutch side seal went out and it didn't smoke until I hit higher revs. It is easy to replace, take off the clutch cover, the clutch and the crank gear. I used a hook type tool to carefully pry out the seal. Put the new one in the freezer for a while and install it using a large socket (closest size to the OD of the seal.

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gorgon thanks, thats the most help ive received on this bike and ive posted on three separate sights. My air screw was only a half turn out will try two. Oil is 900ml i found out, changed out the oil, not sure it had ever been changed. running 1:32 on gas mix. Went back through carb to make sure it was clean. probably the simplest carb ive ever rebuilt. ill have to figure out the float height.

Also put some high temp silcone stuff around the carb boot where it sits in the square frame. that bolts down. just in case. Ordered the seals for left and right sides but they may not come in until monday. if they dont how bad would it be to ride it the way it is if it is the seals?

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got the carb back on, exhaust all tight, two turns out on airscrew, float around 22.5mm. Not as much smoke but still some. Not sure how much these old bikes smoke. Also some bad news possibly. Sounds like some rattling in the cylinder. Are these motors usually noisey or?

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Hold the bike up straight and fill the oil slowly until the level is up to the threads on the fill hole.

Not the fill hole! I think you're talking about the check hole...

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got the carb back on, exhaust all tight, two turns out on airscrew, float around 22.5mm. Not as much smoke but still some. Not sure how much these old bikes smoke. Also some bad news possibly. Sounds like some rattling in the cylinder. Are these motors usually noisey or?

There's gonna be some smoke, your burning oil with the fuel after all. Go watch some old MX videos on YouTube to get an idea of how much smoke is "normal".

Aircooled cylinders are always much noisier than watercooled ones. How much noise is normal is hard to gauge without experience. Maybe find somebody who knows these bikes and have them listen to it, or record a video and put it on here, then we can help.

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well the "rattling" to me is too loud. i could be wrong, never had a 2 stroke. Any suggestions for break in? Ive heard different ways from taking it easy to moderatley riding and throwing in some higher rpms and wot to set the rings.

heres a video of someone elses cr480. thats about how much it smokes.

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Not the fill hole! I think you're talking about the check hole...

No the fill hole. Do you own one of these? It is tough to get all 900cc in.

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A little rattle is normal for a finner. I say ride it, mine sounded bad and I raced it all season with no issues. Like I said, make sure you have GOOD fuel in it.

Nice looking bike, frenchman.

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They don't like fuel laced with ethanol. I suggest either 100LL avgas ($5 a gal at your local airport) or race fuel. Or, go to the Honda dealer and buy 2 head gaskets. Install those,and it will run well on any fuel.

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gotcha well i suppose ill go with a double head gasket. any info on flwheel weights? how would i do my own? I have a welder just not sure how to balance it or how the process of that would go.

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Also are there any tubes that should be connected to the carb besides the fuel line? what about the line on top of the tank cap?

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Increasing the flywheel weight will help keep that 480 from stalling. (Even though those bikes are still stallers)

The video you showed was too much smoke in my opinion. Not to worry though, since you just bought it. Might take a while to undo whatever the previous owner did to it. I think the bike in the video was also idling high. I know several guys (including Gorgon) who race an '83 CR480 and none of theirs idles that high or smokes that much.

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gotcha well hopefully my new seals get here tomorrow so i can get out to the dunes sat. Should I put grease on them or anything before installing?

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