Jump to content

TTR 50 run w/o oil, won't start

Recommended Posts

I think my son ran his motorcycle without oil.  It was running perfectly fine, then wouldn't start.  Found oil in inlet filter.  Almost no oil left in crankcase.  Put new oil in.  Engine turns over fine, but won't start.  Spark plug is working fine.  Only getting about 30psi compression with starter motor.  Won't even fire with starter fluid.  

Looking for recommendations for next steps and have a few questions.  What are possible problems with this engine (extent of damage)?  What's most cost effective: repair engine, replace engine, replace motorcycle (assuming work is done by MC shop)?  I could probably do it myself, but not sure I'll have time.  If that's the only economical method, I will.  Can I get a whole new engine as a drop in replacement?  Where's best place to get parts?

Thanks so much.

Share this post


Link to post
Share on other sites

Did you drain the oil to see if there were any metal bits in it?

Chances are the lower end is ok, but the top end will need work.  you either need rings or valves or both. Can you do the oil test and see if the compression goes up?

 

  • Like 1

Share this post


Link to post
Share on other sites

Good call on checking the oil.  I put new oil in it yesterday, wasn't really any old oil to drain.  Drained all the oil today.  It was pretty dark, especially considering I only put it in there yesterday, and obviously the bike didn't run.  No obvious metal chunks.  I ran a rare earth magnet through the drained oil, and I only got out a couple of very small metal bits, nothing I would normally be concerned about.

By oil test, I believe you mean put a little oil in the cylinder and see if that helps compression.  I'll try that next and let you know.  Here's to hoping.

Share this post


Link to post
Share on other sites

Drop the float bowl chamber or, if there is a big nut on the bottom, take it off, remove the pilot jet and see if it is plugged up.  Hope that it is so you can just clean it out and when you replace it the engine will start. 

  • Like 1

Share this post


Link to post
Share on other sites

He tried with starter fluid, no go, its not the carburetion, its the lack of compression.  Possibly just rings and a valve job, might need a new piston, maybe a new head, will have to take apart the top end to know for sure, not difficult work if you have the time.  How old is he? Time to introduce him to wrenching?

  • Like 1

Share this post


Link to post
Share on other sites

He's almost 6.  I think he'll enjoy wrenching on the bike, me not so much :)  Thanks for the tips.  Glad to know there's hope for the bike.

Share this post


Link to post
Share on other sites

Try a leak down test.

If you hear air coming out the intake, then your intake valves are leaking.

If you hear air coming out of your exhaust, then your exhaust valves are leaking.

If you hear air coming out of the crankcase/etc, then your rings are leaking.

  • Like 1

Share this post


Link to post
Share on other sites

Here are as found pics of the piston and cylinder.  Is this more than normal wear?  The piston and cylinder still seem round based on my measurements.  There is obvious scoring on both that can be seen in the pics.  Seems like I should replace both, but want to make sure that's not normal wear.  I've got .25mm total clearance between piston and cylinder.  Service manual says normal is .03-.04mm, max .15mm.

Thanks

IMG_7802.JPG

IMG_7805.JPG

Share this post


Link to post
Share on other sites

I can feel some slight scoring on the cylinder.  It's in the same area as the wear on the piston.  It's not as bad as the scoring on the piston, but it's there.

Share this post


Link to post
Share on other sites

Ya that thing is toast, get the cylinder honed out buy a new piston & gaskets while your in there id check valve clearence and it will be fine after that

  • Like 1

Share this post


Link to post
Share on other sites

Cylinder and piston are definitely no longer serviceable.  Cylinder may be repairable, I don't know if those are plated, sleeved or plain cast iron. 

I would check the cam and journals for scoring as well.

  • Like 1

Share this post


Link to post
Share on other sites

New cylinder is $120 on partzilla.  Try bringing into a machine shop or two in your area to see if they think they can repair it for less. If you are lucky, they can run a hone through it for pretty cheap and still have it back to service.

Replating costs significantly more, but you can try calling Millenium Tech or Power Seal USA.  But quotes I got were well north of $120.

  • Like 1

Share this post


Link to post
Share on other sites

+1 on checking the cams, & journals.  Those are probably toast if your piston looks like that.

Also - pick up some assembly lube for when you put everything back together.

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)

Hey, it is a mistake. He is young and may not know how the bike needs oil.

The piston is beyond shot.. Replace the rings as-well. I do not know much about cylinders but you may need a new one or try to re-hone it.

Don't be worried. A pistion and rings can be replaced same as the cylinder.

While your at it, see if the crank has any up & down motion. Also check your valve seat or heads.. They may or may not need replacing.

Where it stands you need:

Piston, Re-Working of Cylinder or New, Piston rings, Gaskets.  To access these amazing websites are; partzilla.com or rockymoutainatvmc.com both of those websites sell OEM parts, good turn around time to get your son back on the dirt.

Keep us posted!

Edited by RipThatYZ250f
  • Like 1

Share this post


Link to post
Share on other sites

So I've ordered a new cylinder, piston, piston rings, and gaskets.  I went through Babbits just because partzilla didn't list a 2018 and I don't know enough to be confident the previous versions are compatible.  Waiting for parts to come in.  I'll let everyone know how it goes.  Anyone have any input on using Babbits for parts?

Share this post


Link to post
Share on other sites
1 minute ago, johnensd said:

So I've ordered a new cylinder, piston, piston rings, and gaskets.  I went through Babbits just because partzilla didn't list a 2018 and I don't know enough to be confident the previous versions are compatible.  Waiting for parts to come in.  I'll let everyone know how it goes.  Anyone have any input on using Babbits for parts?

Never heard of babbits, a simple search and their website popped up. 
They look to be fine, there isn't any worry about these online retailers because you can always refund them easily through card holder etc.

Great to hear you ordered some parts.. I would love some more updates on when you build it back up.
Keep us updated :)

  • Like 1

Share this post


Link to post
Share on other sites

For future reference, the Yamaha part number is the same at any dealer.  So you could have gotten it on Babbits, ThumperTalk, RockyMountainATVMC, or Partzilla, and plugged it into any of the sites.

 

Keep us updated! :)

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×