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Help, crf70 running like crap

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Wondering if you could help me out, I have a 2005 crf70 my second son is on only mod is an endcap for the exhaust, it has run flawless till today.

Will not idle and when holding at 1/8 to 1/4 throttle to make it run it coughs and intermittently backfires through the carb??? Same tank of gas as when running good. Could it have fried a valve or timing chain maybe shot? I will compression test tomorrow once back at shop.

Suggestions appreciated.

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If the valves check out good, take a look at the ground wire by the carb/air cleaner to see if it's well grounded. If that's OK, pop off the left hand side cover and see if the pick up coil has some debree on it and if that checks out OK, try popping in a new plug and pull the carb and give it a good cleaning taking special care that pilot jet is clear.

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Thanks guys, intake was tight, I opened it up to spec, cleaned the carb and it runs much better now. I'll check out the pickup for debis and I had the ground off so maybe that was part of it too.

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Thanks guys, intake was tight, I opened it up to spec, cleaned the carb and it runs much better now. I'll check out the pickup for debis and I had the ground off so maybe that was part of it too.

Good to hear, thanks for keeping us posted!! :thumbsup:

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I just got a used 06 crf70. Not running very well at all so before taking anything apart to clean or adjust, I pulled the plug- threaded in comp gauge and kicked it about 4-5 times. Went to 65-70psi and thats it. Bike has sat for a couple hours and still reads same, 65-70psi. Guy at local shop said it should be around 120. Is that about right?...and if so, check valves or rings on piston or both? I'm really only familiar with 2-strokes.

Any feedback greatly appreciated!

Thanks- Doug

Nashville, TN

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I just got a used 06 crf70. Not running very well at all so before taking anything apart to clean or adjust, I pulled the plug- threaded in comp gauge and kicked it about 4-5 times. Went to 65-70psi and thats it. Bike has sat for a couple hours and still reads same, 65-70psi. Guy at local shop said it should be around 120. Is that about right?...and if so, check valves or rings on piston or both? I'm really only familiar with 2-strokes.

Any feedback greatly appreciated!

Thanks- Doug

Nashville, TN

Check the valves, unless it's been ran out of oil or overheated the piston and rings should be Ok.

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will do- thx! .004 is good both both valves right? Also- do you know what the normal compression should pump up too?

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