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Yamaha Blaster - No Compression

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  • Yamaha Blaster - No Compression

    I know this site has a ton of sand car and SxS topics but how about a quad topic. I’m going to have to tear down my sons Blaster AGAIN and have the top end re built. Now I’m no mechanic. Think LRS but completely opposite. But I’ve got a service manual and YouTube so I got this.

    I bought my son a 2001 Blaster off of board member in October of 2017. The bike sat for years before so I’ve got no clue if/when it was last re-built. He had the carb gone through and wanted to sell it. It had a great price tag so if I had to re-build it, it wasn’t a big deal.

    First trip out to in January of 2018, it would would run fine while it was cold but would die when it warmed up. Had very little compression when warm. Figured the the rings were bad or it needed to be bored. My brother in law and I tore it down and it was warped so I took it to Q&E in Anaheim to have it bored 1 over. I wanted to keep it as close to stock as possible for my son who is still learning to ride.

    Got it back a month or so later and put it together for our summer trip. Also did the oil block off kit and new reeds. We did 10 days of riding with zero issues. Did the proper break in per the manual/internet and everything ran great. Ran it 40 to 1 oil/gas and checked the plug every so often to make sure it wasn’t leaning out. Couldn’t get out for our first Glamis trip until Super Bowl weekend due to my work obligations. Bike ran fine on Friday with zero issues.

    Saturday on the way back from the swing set, we were cruising along Gecko with the wind. So there was very little air flow to the front of the bike to cool it. I was driving the RZR and the fan even kicked on. So I was a little worried about the Blaster overheating. I stopped him a couple of times and it was warm but nothing terrible. He gets it back to camp, eats some lunch and wants to ride around. No start. I go out and kick it and immediately feel there is little compression. I didn’t want to pull the plug that day because the wind was blowing terribly and I didn’t want sand getting in the top of the head. Sunday morning I pull the plug and it’s black as can be.

    Now my questions: if I leaned it out, wouldn’t the plug be completely white? Is 40 to 1 a good gas/oil mixture? The manual calls for 20 to 1 but that just seems overkill. I ran a 250r I had for over a decade at 40 to 1 and my buddy runs his 85 Honda 250r ATC at 50 to 1 since they day he got it in 86. Did my son just get it too hot? Wouldn’t it had to be close to 325 degrees before it starts to warp the side walls?

    My goal is to get it running, sell it and buy him a 4 stroke Honda 250x or 300ex. Something a little more reliable and I don’t need to mix gas for one bike only. I’ll update this post as I tear down the bike and put it back together.

    Click image for larger version

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  • #2
    I’d run it at 32:1. Make sure you are putting a good piston in it and not a Chinese one. Make sure you bore it or hone it real good. Also make sure your crank seals are good. And make sure your air filter is cleaned and sealed well.


    • #3
      Air cooled 2 strokes are fickle for simple reasons.

      I'll add and support what LLCool said as well...

      Run 32:1 - they need the oil, it is the life of that little motor.
      Check for air leaks that would cause the motor to run lean, I bet you money you'll find the piston melted off one side of the top (Been down this road myself).
      These quads and their trany are meant to be shifted often, long steady rides at speed are gonna heat up your motor, you already knew it was a hot day.
      Don't use the knock off copies piston and rings, they are cheap and fail easy (Been down this road myself).

      Good thing is its an easy fix and fairly cheap.


      • #4
        I used a Wiseco piston the last time. Will probably do the same on this one. I’ll look for air leaks. Thx guys.


        • #5
          Blasters are fickle rides. My cousins and I all grew up on them and we had about 5 of them in camp at one time. 4 of them would blow up every trip. Mine never lost the top end for some reason, maybe it was luck, maybe it was a proper mix, maybe I just didn’t ride it hard enough (very doubtful). We always mixed my bike at 32:1, no other real tricks to be mentioned. Hope you can get it worked out!


          • #6
            I began tearing it down yesterday afternoon.

            My helper for the day.
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            Here is what I found. Cylinder looks to be scorched. You can see it on the sides. Sorry for the poor quality pics and the top of the piston and cylinder head had already been wiped down when I took the pics.

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            Pulled everything apart and will take to Q&E in Anaheim when I’m down there for a meeting on Tuesday. Kind of in a rush now since we tentatively planned a trip for St Patrick’s day.

            Attached Files


            • #7
              Spark plug, piston top and head all look fine.

              I'd say by the cylinder scoring the way it did....simply means hot day, long ride steady throttle at speed and simply not enough oil/gas mixture.

              Replace and go 32:1, that has always been a safe place for air cooled motors, stock mixture is 20:1 so keep that in mind.

              From the vast internet and its pretty spot on for oil/gas ratios.

              If you mix it 40:1 with regular mineral 2 stroke oil, you will blow it up. If you mix it 40:1 with synthetic oil, you will be fine.

              The Blaster came with oil injection. If the Blaster is in stock condition, you don't mix the oil in the gas; you put the oil in the oil tank. So I assume the oil injection has been disconnected and that is why you are asking this question.

              If you use regular mineral 2 stroke oil, which is the standard oil that you can buy at any store, the ratio is 20:1. That is 6 1/2 ounces of oil per gallon of gas.

              If you use a good synthetic oil, such as Golden Spectro, Bel Ray MC1, Duralube, PJ1, etc., the ratio is 50:1. That is 2 1/2 ounces of oil per gallon of gas.

              If you use Amsoil, the ratio is 100:1.

              The best oils to use are Golden Spectro, Bel Ray MC1, and Duralube.


              • #8
                Now I'm curious what brand oil mix did or do you use?


                • #9
                  Originally posted by Squashy View Post
                  Now I'm curious what brand oil mix did or do you use?
                  Golden Spectro.


                  • #10
                    I actually put it back together, took some pics and am trying to sell it without replacing the top end. I’ve been looking to get him in to a Honda 250 or 300. If I can’t get a decent price for it, I’ll re build it and attempt to sell it.

                    We got a St Patrick’s weekend trip planned so time is a little tight. I’ve gotten some interest today but no cash. I only bought the bike for $400 and re built it once so I’m only in to it for $700 or so.



                    • #11
                      Went to a new home today. Now I'm on the hunt for a Honda 250 or 350. Also heard great things about the Raptor 250 but can't seem to find many for sale.


                      • #12
                        Don’t get a Raptor 250, it’s slow as snail shit. Look at the Raptor 350 at a minimum.

                        There are a bunch of used 350’s around. Not mine, don’t know the seller but here is one on Craigslist.



                        • #13
                          Got him a super clean Honda 300ex. Going to find some paddles for it and he should be good to go.

                          Click image for larger version

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                          Last edited by AHW; 02-16-2019, 01:20 PM. Reason: Edit to add pic


                          • #14
                            Can’t go wrong with a 300ex. Congrats