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MannyIsle

1990 TRX300FW - Smoke from top of motor

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Hi, just purchased my first ATV (an oldy) for some snowplowing. I've taken it for a few short runs and I've noticed that the top end of the motor (cylinder) begins to smoke (whitish smoke) after riding for 5-10 minutes. There is no smoke coming from the exhaust, and it doesn't smoke on startup. Also, the overheating light doesn't come on to indicate any issues with heatTrying to figure out if it's just burning off water or old oil from the exterior of the motor, or if there is a bigger problem I may need to address.

Thanks!

image.gif

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you need a service manual 
 

Possibly oil leak from the rocker box cover or valve cover. Note: do not over torque any of those bolts or you’ll  strip the threads.

 

possibly overheating and burning off old oil; is the engine really hot? If your oil light is not coming on you need to replace the oil temp sensor and/or the alarm box
 

you’re going to have to figure out where the smoke is originating.

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Welcome to the forum!

Great little machine will last forever with a bit of maintenance

It may have a small leak at the valve cover? check with flashlight-its pretty common

Need to determine if it looks/smells more like steam from water or smoke from oil

If you just bought it, the owner could have pressure washed it and might have a bit of water up top boiling off

If it is valve cover, a great time to adjust valves and seal up valve/rocker cover

 

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11 hours ago, MannyIsle said:

Hi, just purchased my first ATV (an oldy) for some snowplowing. I've taken it for a few short runs and I've noticed that the top end of the motor (cylinder) begins to smoke (whitish smoke) after riding for 5-10 minutes. There is no smoke coming from the exhaust, and it doesn't smoke on startup. Also, the overheating light doesn't come on to indicate any issues with heatTrying to figure out if it's just burning off water or old oil from the exterior of the motor, or if there is a bigger problem I may need to address.

Thanks!

image.gif

welcome to the forums , there is a sealing washer on one of the bolts of the rocker box of the 300 , it is located at #19 on this print , it may be missing from some previous work ------------ could also be leaking from the decompression lever shaft seal , or the rubber  cam end cover or a few other spots around the rocker box 

image.png

  

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Check also for leak or puddled fuel on the rocker cover—from fuel tank.
White smoke isn’t usually oil, but it can be in small amounts. 

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Thank you so much for all of the input. The oil light does work, as it comes on for 1-2 secs when I turn the key to the on position.

 

I'm going to try and let it run for awhile this afternoon and see if I can pinpoint where the smoke is coming from. I took a few photos and it does look a bit oily at the top end, and this might be the culprit as the oil burns off.

 

 

motor1.jpg

motor2.jpg

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Don’t use either of them they’re so abbreviated and a lot of the information it’s just combined and jammed together

You can go to the service manual area here on the Forum and download the actual Model specific Honda factory service manual, they are superb and cover everything from basic maintenance all the way up to a complete engine tear down and rebuild

Here is the link to the TRX300FW manuals

https://drive.google.com/drive/mobile/folders/1GcqS65GYd3yFmEAGsI7LP-eZp2jMRVJU/1eqVb5JW5em4PBbDrgHsRbhFKH5rFr75l/1vG2Up48bgvpVgopy-jLg5p1AKUWQnypf/1xPtIRTon47rnmYmqflFS5d8LqLeuZlql?usp=drive_open&sort=13&direction=a

(Man I don’t know why that link is so long…)

Edited by AKATV
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Yeah I don’t like either clymer or Haynes.

i got the Honda ecopy and then bought printed copy off fleabay.

 

you’ll want the 88-94 honda trx300 manual 

sometimes you see 88-90 or 88-91, etc. these manuals printed before intro of later models. These OK too but latest revisions are better 

 

 

wow that thing looks oily!!!

Edited by Goober

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The Honda factory service manual is amazing! Thank you for providing the link. Just want to say that this forum has been such a great help, thank you!

 

45 minutes ago, Goober said:

Yeah I don’t like either clymer or Haynes.

i got the Honda ecopy and then bought printed copy off fleabay.

 

you’ll want the 88-94 honda trx300 manual 

sometimes you see 88-90 or 88-91, etc. these manuals printed before intro of later models. These OK too but latest revisions are better 

 

 

wow that thing looks oily!!!

 

Ya I'm going to clean off all that oil and see if it helps me identify where the leak is coming from.

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Very good. To inspect and clean You’ll have the remove the fuel tank. Two plastic tabs, 1 bolt and a fuel line. i usually drain it first (but you don’t have to) by using a tall funnel and fuel can:
close the petcock 
disco the fuel line from the carb or petcock 

drain the tank

Remove the kick start cover 

Disconnect the plastic fender tab (left side) from the tank. Very important or you’ll break the fender.

remove rear tank mount bolt.

ensure rear of tank will rotate slightly upwards easily.

Grasp front of tank forward of fuel cap

Tank rotates rearward and upward from two frame rubbers (see diagram)

 

clean off oil using penetrating oil, brushes and rags. Don’t want you using strong solvents on anything exposed, like gaskets plugs paintwork and aluminum 

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1 hour ago, MannyIsle said:

The Honda factory service manual is amazing! Thank you for providing the link. Just want to say that this forum has been such a great help, thank you!

 

 

Ya I'm going to clean off all that oil and see if it helps me identify where the leak is coming from.

i'll save you the trouble. clean it all off the top of the engine, go buy a tube of yamabond or hondabond ( DO NOT USE RTV SEALANT ! ), get yer hands on the oil seal for the decompression release lever, the o-rings that go in the valve inspection caps ( 2 ), and there is two small o-rings that are around the rocker shafts ( slotted ends on spark plug side ) that will need replacing ( very common to leak oil ). the hardest part you will face is getting the rocker shafts out of the rocker box, reason : they are held in place by dowel pins ( or used to be ?), and can be tricky to remove. what i do is clamp these pins in my bench vise, slowly turn the rocker box back and forth, while i pull up on the rocker box, this allows me to remove the pins. once the pins are out of the rocker box, then you can pull the rocker shafts out of the rocker box, PAY CLOSE ATTENTION TO WHICH ROCKER GOES WHERE !.

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8 hours ago, MannyIsle said:

The Honda factory service manual is amazing! Thank you for providing the link. Just want to say that this forum has been such a great help, thank you!

 

 

Ya I'm going to clean off all that oil and see if it helps me identify where the leak is coming from.

You are welcome, this is the a great place for help and advice

Let us know what you find and how you make out

See you around!

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