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Very rough running on decel

colriverrat

Contributing Member
"I just put new pistons and ri

"I just put new pistons and rings in my 1980 DT65. It seems to idle a little rough, but runs. It will Idle like that till it runs out of gas. BUT as soon as I throttle it up and try to come back to idle it surges, bucks, spits and dies.

After it dies on decel it is hard to restart. It also runs real rough and sputters at around 1500 rpm. If I give more throttle and get the rpm up past 2000 it runs great.

The plugs are dark but I blame that on the 25:1 break in mix. Could it simply be loading up from the 25:1 oil mix?

I have 2 sets of idle jets 85 & 67.5 the problem exists with either set of jets."
 
"Did you correct the problem t

"Did you correct the problem that led to the rebuild in the first place?

Sounds like the carbs had something to do with that - you did rebuild the carbs as well to protect that newly rebuilt power head, didn't you?"
 
"I did go through the entire f

"I did go through the entire fuel system. The carbs have been cleaned, jets removed, soaked, blown out W/compressed air. floats, needles & seats new. Factory fuel pump replaced with electric, flows awesome. New fuel filter. All fuel lines replaced. Fresh Suzuki oil and 89 octane gas.

The reeds are still original but they appear perfect. I cannot even slide a .002 feeler gauge under any of them.

I'm really scratching my head??? Spark HURTS when boot is pulled. Do I dare try going up one heat range till the 25:1 mix is gone???

The poor running is from idle to about 1800 RPM, on the way up or down. It is strong as an ox all day above 1800 rpm."
 
Joe I thought you had that thi

Joe I thought you had that thing all dialed in? Did you re-synch carbs when you put them back on.
 
"I did synch the carbs, this w

"I did synch the carbs, this was a little tricky. The liquid kept bouncing back and forth. I used a homemade manometer with 20' of 5/16 clear tube.

I'm starting to wonder if the reeds are bad. About 1/2 make a slight "crinkle" noise when I push them lightly from the carb side. I ordered a set of Boyesen's, I'll put them in next week.

I did not use any type of gasket sealer on the reed plate and intake gaskets. When I do the reeds I'm using RTV.

I did forget to check the timing, it was off about 4*. Have not run it since I fixed that."
 
"Update:
The timing did cure


"Update:
The timing did cure 90% of the problem. I still have a spot around 1200 RPM where the motor surges badly. A very slight move up or down in RPM and it runs fine.

Could the reeds cause this "Flat" spot? I have the 67.5 Pilot jets in it now, should I switch to the 85's?? The 85's are what the same year 50HP call for. Could the manual be wrong and reversed the numbers? I cant believe the 50HP would run larger pilot jets than the 65HP."
 
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