XR70 slight Pop on decellaration

I was cleaning up my 10 Y.O.'s 70 last night and adjusting the chain, and noticed a slight Pop on throttle down or down shifting. I tweaked the mixture screw to find start and end of highest idle, then set 1/2 way between. This setting is about 1 3/4 turns out, and it helped, but still has a little pop. Any ideas?? Only mod was to cut rear 1/3 of air filter ball off.

Adjust your valves, make sure exause bolts are tight, use higher octane fuel, use lower octane fuel.

Do you by any chance have the valve specs for an 03 XR70 handy, and hot or cold? thx eds

The valves are supposed to be set with the engine completely cold. Honda says to adjust them to 0.003-0.005 mm. Go to BBR for a video to help you.

mms://media.bbrmotorsports.com/How_To/Windows/CRF50_ValveAdj_Win.wmv

I'm sorry it's not a link. Copy and paste it into the address bar.

Thanks guy, thats exactly what I needed. I was curious about finding TDC on one of these little motors (I've done it several times on my 400), but that explains it well.

Glad to help.

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