dolphinguy Posted November 18, 2011 Share Posted November 18, 2011 hello again. have 1979 toy dolphin with 20r engine.it has about 78k on it. when i start it up it will leave a black carbon looking spot in driveway. after 2-3 minutes it stops and no more driveway stains. any ideas. thank you d g Quote Link to comment Share on other sites More sharing options...
90toydolphin Posted November 18, 2011 Share Posted November 18, 2011 i assume you mean the exhaust itself causes the spot, ie black smoke comes out. i remember being told that if it's black smoke it's probably some oil leaking into the cylinders and burning off when started. if you are using a little oil this could be it. white smoke was usually water vapor, could be caused from condensation while sitting or a leak from your cooling system into your combustion areas. if it's a coolant leak you should be adding coolant once in awhile. can't be too bad if it is still running ok and the smoke stops. one thing for sure is if you are using a little oil you know the oil pump is working ). if it under the rig where the spot shows up you probably have a hole in the tail pipe. Quote Link to comment Share on other sites More sharing options...
dolphinguy Posted November 18, 2011 Author Share Posted November 18, 2011 i assume you mean the exhaust itself causes the spot, ie black smoke comes out. i remember being told that if it's black smoke it's probably some oil leaking into the cylinders and burning off when started. if you are using a little oil this could be it. white smoke was usually water vapor, could be caused from condensation while sitting or a leak from your cooling system into your combustion areas. if it's a coolant leak you should be adding coolant once in awhile. can't be too bad if it is still running ok and the smoke stops. one thing for sure is if you are using a little oil you know the oil pump is working ). if it under the rig where the spot shows up you probably have a hole in the tail pipe. the spot comes from the tailpipe out of the side. also uses no oil or do i have to add coolant.yes it runs great.it does get lousy gas mileage though.like 10 per gallon. Quote Link to comment Share on other sites More sharing options...
5Toyota Posted November 18, 2011 Share Posted November 18, 2011 black smoke sounds like it may be runing a little too riche maybe overchocking that causes excessave gas consumtion loo kat the glass window on the carb at runing idle gas leval should right in the middle of the glass no higher would spray clean the chock e i used too set the mixtur with a portable tac very carfully turnin mix screw little ata time at a warm idletell eng starts too slow then liston and watch the tac as you turn it back out slow at a moment too stablez until you get toohigest rpm you can get on the tac if the idle speed drops you went too far then adjust the idle speed screw if the carb does not adjustgood may need rebuild black smoke is almost certainly a sign of too rich oil burning is usely blue smoke my twenty r minimax get 15to 17 had 20r wagen and truck get that stration out gas miles should a lot better i tend to forget young people maybe not familer wit carbs old like me not with computor lol Quote Link to comment Share on other sites More sharing options...
mulwyk Posted November 18, 2011 Share Posted November 18, 2011 I had that black spot thing on my '84 Sunrader/ 22R engine. It would idel too fast on a cold start and leave black on the driveway. It was a sticking choke. You can tell if you have a sticking choke by taking off the air cleaner cover and actually looking into the top of the carb. On a cold engine, the choke should be closed (horizontal) before you start the engine, then, after the engine starts, the choke should gradually open and be completely open (vertical) within 10 seconds (?) or so. Quote Link to comment Share on other sites More sharing options...
tumolt Posted November 18, 2011 Share Posted November 18, 2011 The problem is with your oil rings. They were not sufficient enough from the manufacturer. Hence you get oil consumption from burn off. I bought a set of 4 pistons and rings off of ebay. I removed the head, removed the pistons and rods keeping the rods in the order in which they go back in, put the new pistons and rings on the rods, and re-installed them. The oil rings are thicker on the newer pistons and now I drove 1000 miles since then and no oil burnoff. This was a factory defect. You may want to get new crank bearings because of the mileage on your motor. You also have to hone the block before putting the new pistons and rings in your motor. WARNING: Do not buy original Toyota piston and ring sets. Get the aftermarket ones. You'd only be putting back defective piston and rings if they were original Toyota pistons. Hope you get it straightened out. Matt Quote Link to comment Share on other sites More sharing options...
wistoy Posted November 18, 2011 Share Posted November 18, 2011 All the replies are good, but if it is litteraly a small spot on the driveway, it may simpliy be condensation coming out your tail pipe. Very comon in WI. winters. For every gallon of gas you use it creats 9 gallons of water, and if your exhaust is cold it will condesate in your exhaust and leak out. (this will not smoke) The black is from the water washing out your exhaust pipes. This also makes intersections and areas at our stop signs very slipery. hello again. have 1979 toy dolphin with 20r engine.it has about 78k on it. when i start it up it will leave a black carbon looking spot in driveway. after 2-3 minutes it stops and no more driveway stains. any ideas. thank you d g Quote Link to comment Share on other sites More sharing options...
dolphinguy Posted November 19, 2011 Author Share Posted November 19, 2011 All the replies are good, but if it is litteraly a small spot on the driveway, it may simpliy be condensation coming out your tail pipe. Very comon in WI. winters. For every gallon of gas you use it creats 9 gallons of water, and if your exhaust is cold it will condesate in your exhaust and leak out. (this will not smoke) The black is from the water washing out your exhaust pipes. This also makes intersections and areas at our stop signs very slipery. thank you for all the help.i will start with the easiest. i'm very glad i found this site. Quote Link to comment Share on other sites More sharing options...
5Toyota Posted November 19, 2011 Share Posted November 19, 2011 wistoy that is also a very correct answer and reason another carbs are dissapiring less tailpipe emissions never heard of the ring thing but i run 2050 oil in all high miles eng have for last 40 years Quote Link to comment Share on other sites More sharing options...
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