Exhaust is getting really hot G1

[mike w]

I have a Yamaha G 1 when we are out for a drive which usually lasts for 30 min or longer the front of the body by the muffler is getting really hot so much so you can barely touch it, is this normal? I do premix but the mix is 70:1 ratio I've thought about making a heat shield any ideas would be much appreciated. Thanks Mike

[DakotaEight]

I would start with the proper mix for that engine. If thats the proper mix then i would move forward from there. It cant be the coil getting to hot as 20 seconds wont do that. Maybe fuel supply? Just my thoughts here. G1G9 or Sho can hook you up with a better answer than me, just so ya know. Many others on this site have such great insight, and dont waste an option or you might miss the fix.

[slonomo]

I'm going to assume that the cart is "running well"?

If so, then.....70:1 is very oil rich. The factory oil injection system mixes at between 150:1 and 300:1, according to the factory service manual. I used to mix at 85:1 and that was too much oil, produced too much smoke and oil dripped from the exhaust pipe. I switched to 100:1 and it was much better. But what was also important was the type of oil I used. I ended up with Echo brand 2 cycle oil for air cooled engines. Make sure you are using the proper oil, needs to be for air cooled engines. Also, if you have been running that 70:1 mix for a while, your muffler is probably coated with oil inside. I would suggest you bbq your muffler if that's the case, this will burn all the oil out. Another thing is that some of the Yamaha G1 mufflers had a fiber type sound deadening material inside the mufflers, as some have discovered by cutting them open. If it does, it's probably clogged. The more recent mufflers did not have that material.

My 2 cents....

[Spicyunicorn]

Have you done crank seals? Very common issue with these one could be starting to go bad causing a lean condition lean=hot

[rmoss]

Originally Posted by Spicyunicorn

Have you done crank seals? Very common issue with these one could be starting to go bad causing a lean condition lean=hot

Don't bad seals cause a high idle condition?

[rmoss]

Just as a side note about fuel/oil ratios; most people are under the assumption that more oil causes a richer fuel condition when the opposite is actually true. The easiest way to understand this is to think of the carbs. fuel jet as a funnel. If you pour oil in the funnel it goes through slowly, where as if you pour gas in it, it will go through much quicker (I.E. richer mixture).

[Spicyunicorn]

Bad seals won't cause high idle condition...... your statement is true thinker oil premix will cause a lean condition but not because of your "flow" theory a 70:1 vs 100:1 is mixed so thin they will flow the same amount of fuel even in that small jet the thicker oil ratio leans out because you have more oil and less gas travelling through the that jet that being said 70:1 isn't a thick enough ratio to cause a lean condition I ran 5 gallons of that ratio after a rebuild and didn't have problem with hot muffler....I would BBQ the muffler like slo suggested and switch to 100:1 premix ratio it seems the ratio (including me) everyone is running

[mike w]

All thanks for the replies The seals have been done about 2 years ago. At the 70:1 ratio the cart doesn't smoke. The cart runs great with governor ground gps on my phone it runs 20-21 mph on a flat surface. One thing I did leave out is I did add a flex pipe to go over the end of the muffler because the wife complained of the smell. I did this to run the exhaust out the back. As far as the muffler being clogged wouldn't I see a lack of power? I had the governor linkage come off the flap on the muffler once and it barely made it back home with a loss of power. Where is the best place to buy a new muffler ? I'm in the process of making a heat shield. Thanks again for all of the help. Thanks Mike

[rmoss]

Originally Posted by Spicyunicorn

Bad seals won't cause high idle condition...... your statement is true thinker oil premix will cause a lean condition but not because of your "flow" theory a 70:1 vs 100:1 is mixed so thin they will flow the same amount of fuel even in that small jet the thicker oil ratio leans out because you have more oil and less gas travelling through the that jet that being said 70:1 isn't a thick enough ratio to cause a lean condition I ran 5 gallons of that ratio after a rebuild and didn't have problem with hot muffler....I would BBQ the muffler like slo suggested and switch to 100:1 premix ratio it seems the ratio (including me) everyone is running

Sorry on both cases you are incorrect. I was a Yamaha motorcycle mechanic and franchise owner for 15 years and it is common knowledge for professional techs. Could be you missed the high idle not understanding we are talking about a 2 cycle engine.

[Spicyunicorn]

Agreed highher premix leans out a motor agreed to disagree on why.....a faulty crank seal will lean out a two stroke motor (run hot or hot enough to score piston) and if faulty enough will allow enough air in to kill the vacuum pulse required for the fuel pump to function thus motor won't run at all... can you explain to me how a faulty crank seal will cause a high idle condition?