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Post Info TOPIC: Leaking base gasket - should I be excited or disappointed??


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Leaking base gasket - should I be excited or disappointed??
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Hello knowledgeable peeps

I have just discovered the base gasket under the barrel is leaking oil - only very slight but sadly it is none the less. I say sadly, but what an excuse to finally pull apart and rebuild a motor (top end), and accidentally make it a 263 while I'm at it. 

Question for you all, I notice reading the post on here from others with the same issue that the bolts for the barrel were loose or not very tight for some. Can you get to them when you take the rocker cover off? I'm guessing the head would have to come off. Anyway thought I'd check their tightness for what its worth.  

 

I've checked the crankcase breather and its not blocked. I need a couple of months to save some $$ and get some time to do it, hopefully it will be ok till then (it has probably been seeping for a while I suspect). I could just do the gaskets but if I am doing this, I can't see the point in disassembling that much without at least new rings, and if I'm doing that then why not another few $$ for a +2mm piston and rebore, valve stem seals and giving everything a clean etc. 

On a side note, a few years ago I would not entertain doing something like this (despite wanting to), but with this site (mainly thanks to Brian's amazing tutorials) I'm keen as mustard to get into it (albeit fairly nervous) and I know I have all you guys here as backup for any questions I have. Feel very lucky to have access to a community like this. 

 

I'm guessing this may be related to slightly drowning my bike 2 years ago, quite a bit of crud ended up in the motor, wonder if it hurt the rings a bit and its getting some blow by. Can't say its lost any power, or uses oil or blows any smoke but maybe I'll be in for a surprise. When I opened the motor recently to do the sprag it looked like brand new in there. 

No doubt I will assault you all with questions in a few months. 

 

Leigh

 

 

 

 

 

 



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Hi Leigh and thank you for your kind comments about the tutorials - it's good to have such positive feedback biggrin

First off, you can only access the external head bolts easily. The internal bolts will require removal of the cam gear to get access so my suggestion is not to worry and go straight to the strip down.

Over the years I have come across a number of TTR engines that have "hydraulicked" following a drowning and they all seem to run OK for a while but further down the line they suffer from oil burning and leaky bottom barrel gaskets. 

I am not a trained mechanic but the conclusions I draw from this is that the piston rings and/or their lands get damaged when the engine slams up against an uncompressible body of water in the combustion chamber.

Also, and again it is supposition, I think the force of impact when the piston stops dead against the water means something else has to give and that the head bolts get stretched slightly. Not in an obvious way but enough to allow the bottom gasket to leak after a while.

Anyone else think those are reasonable assumptions?

I think you have to wait until you have the barrel off before making a final decision but I am suspicious that just fitting new rings will be a long-term fix cry

We are here to help. Let us know what you find.....

Brian



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Hey Brian

Thanks for the advice, really appreciate it. I'll certainly let you know what I find and take photos ( and err no doubt have lots of questions)

When you say just rings might not be a long term fix, are you meaning replace piston as well and maybe new head bolts?

I hope you don't mean bottom end might be dodgy😢

My plan is to replace piston +2mm and rings, new gaskets , valve seals and I guess disasamble the head and clean everything, maybe new head bolts? Probably port and polish the head too while I'm at it.

Leigh.

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Doing the lot is an overhaul and ride again .just rings you may need to revisit and do the rebore ext some time soon 

Brian's theory on water lock up I recon is correct everything is torqued down providing a small amount of stretch with the big hit there may be a bit of give in the bolts threads in the cases ext allowing the slight leak to develop .once re done should be OK  

 



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Makes sense. For the sake of a few hundred dollars I'll do the lot. Probably won't have to touch it for years.......if I stay out of trouble 😜

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If you are following the guide here http://www.ttr250.com/Removing_Cylinder_Head/TTR_head_removal.htm  Leigh then can you please feedback any bits you find confusing or anything missing please?

It is worth mentioning that moisture can sometimes get down the threads of the front left "outside" head bolt so make sure that the bolt and case threads are nice and clean before putting it back.  

I doubt that your head bolts will have been damaged but Steve stocks s/h ones if needed - see https://totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/?ObjectPath=/Shops/699105d9-e4cc-4b32-b236-84e72cd67f84/Products/TTR-0481

Brian



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I will definitely be using those guides, I have a couple of basic questions so far but I will wait closer to the time and once I have done more research reading the manual etc so I don't pester you too much! Happy to let you know what I understood and what might be missing for a first timer like myself :)

I am guessing there is a different head gasket to go with the 2mm oversize piston and rebore? Does the head have to be modified by 2mm as well? 

I will save a few $$ and then buy parts and get into it. I'll add to this then.

Cheers Leigh

.



-- Edited by leigh on Tuesday 13th of June 2017 12:09:21 AM



-- Edited by leigh on Tuesday 13th of June 2017 01:02:14 AM

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Same head gasket fits all up to the max 2mm oversize. 

No need to modify the head in any way. Just clean up the valves, fit new valve stem oil seals and lap the valves in.

Brian



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Great. Roger that.

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