A forum for owners of Yamaha TTR250 trail and enduro bikes!

fwtian · Veteran Member

TTR 250 Top End rebuild

TTRfan · Super Guru

Looks like the engine seized and the piston has picked up some metal from the barrel liner cry

Ref the bit of gasket goo, it is probably not a good idea to have anything floating around in the sump. It is a quick job to take the clutch cover off to remove it. You can also clean the oil strainer whilst you have the cover off.

The flywheel magnet is very strong and makes it difficult to hold it on the I mark. I tend to ask Mrs TTR to come out in the workshop to help at the point that I am replacing the camshafts so that it all lines up properly.

Anyone know a "one man" solution?

Brian

fwtian · Veteran Member

The cylinder is scratched a lot... i hope i can get it fixed at +1mm...

I will try to take the piece out...i hope i can grab it from the cams chains space so i dont have to take off the clutch cover....

Before i start the rebuild i was hearing a loud noise from the top end.. it was like tak tak tak tak :P

When i was at really low RPM i couldnt hear it,but when i was giving a little more throttle the tak tak tak was starting.
I thought it was the piston until i saw that the small piece of metal that holds the camshaft with 2 bolts was put at the wrong way...
The mechanic that i gave him the bike to fix the camshafts timing put it wrong... the inside of this metal that contacts the camshaft is scratched all over...

i know that noise might also come from a problem like this.... is it possible the loud tak tak tak ( :P ) came from this scratches???

TTRfan · Super Guru

fwtian wrote:
i know that noise might also come from a problem like this.... is it possible the loud tak tak tak ( :P ) came from this scratches???

It is unlikely that the camshafts would make that noise unless the caps were loose.

If the engine was run low on oil (which is the most likely cause of a seize) then there is a chance that the noise could be a worn little end. What does the bearing surface in the conrod look like? It needs to be round, with no ovalling, and clean with no bluing or score marks. The gudgeon pin should be a snug fit and not "rock" overmuch.

It is difficult to check the big end bearing but I think it would have given a different noise to what you describe if it was badly worn.

Brian

fwtian · Veteran Member

The Engine run low on oil many times... thats why the piston got seized like that.

but i dont think that rod is the problem... i tried to rock it and it wasnt moving almost at all. I didnt check the surface but i think that if the rod is ok then the crankshaft is ok. (am i wrong?)

also i think The gundjeon pin was moving more than it should be....

-- Edited by fwtian on Sunday 13th of November 2011 04:03:13 PM

fwtian · Veteran Member

One more question!!! When i took off the cylinder head cover oil started to fell from the camshafts space... The camshafts where full of oil... is this normal?? shouldnt it fall down to the bottom of the engine?

The photo was taken after i strained some oil.

Uploaded with ImageShack.us

you can also see on the right the wrong direction camshaft cap!

TTRfan · Super Guru

That is to be expected as the oil doesn't drain from around the caps.

That is a good thing if you have low oil as it protects the valve train for quite a long time. It is usually the piston that seizes up first if you run out of oil which is cheaper to replace than a head, valves and camshaft.

Before starting any engine work, I lean the bike over to get as much out of the head as possible. The rest I remove with a bit of tube on the end of a syringe.

Brian

fwtian · Veteran Member

Thanks Brian! i got a bit scared as i thought something was going wrong!

fwtian · Veteran Member

Brian The TTR cylinder can only be opened at +1mm ?

Oem pistons are +0.50mm and +1mm?? Or it goes +2mm??

-- Edited by fwtian on Thursday 17th of November 2011 06:29:29 PM

TTRfan · Super Guru

I think you are right and the biggest OEM oversize is +1mm

However, it is possible to buy piston kits such as the Wossner in 1.5mm and 2.0mm oversizes - 2.0mm takes the capacity out to a useful 263cc.

The following is a table of the Wossner kits and part numbers:

Piston	Oversizes	Piston Kit
Size	(mm)	Part No.
(mm)
72.95	Standard	8646DA
73.45	+0.5	8646D050
73.95	+1.0	8646D100
74.45	+1.5	8646D150
74.95	+2.0	8646D200

http://www.ttr250.com/TTR_extras/#Wossner_Pistons_-_full_kit

fwtian · Veteran Member

how many mm can the cylinder be opened? Mine is now opened at +0.5mm...i hope it didnt got seized to much so i can buy the +1mm OEM piston... :(

TTRfan · Super Guru

I may have misunderstood your question but the fact that Wossner sell +2mm pistons makes me believe that it is a safe maximum. Having had one bored that size recently I wouldn't want to take much more off the sleeve/liner in any case - see pic of my +2mm barrel below. The walls are quite thin:

/download.spark?ID=962011&aBID=139305

fwtian · Veteran Member

Sorry but i dont know the exact mechanical terms!!! But yes this is what i asked! How many miles you had with the +2mm piston? it it reliable?

TTRfan · Super Guru

Not used it yet. I have been to busy to do any work on my project bike - see http://ttr250.activeboard.com/t43731716/modernising-a-1993-yamaha-ttr250-open-enduro/

I have no reason to doubt its reliability. I haven't heard any horror stories - yet.........

Brian

fwtian · Veteran Member

Guyz i need a quick answer!!!

Does the later blue models OEM piston fit the older white ones??? I need a sure answer!!!

TTRfan · Super Guru

fwtian wrote:
Guyz i need a quick answer!!!

Does the later blue models OEM piston fit the older white ones??? I need a sure answer!!!

YES!!!!!

fwtian · Veteran Member

Thanks Brian!!!!! I am ordering the piston righh now !!!! :D

fwtian · Veteran Member

furious furious furious what will happen if i dont put the washer number 12???? http://www.partforyamaha.com/pages/OemParts?aribrand=YAM#/Yamaha/TTR250_-_TTR250NC_-_2001/CYLINDER_HEAD/TTR250NC_(2001_MOTORCYCLE)/CYLINDER_HEAD_(TTR250NC_-_2001) )

Cubber · Super Guru

Nothing will happen straight away but in time the tension of the head bolt might loosen. cry

Using the washer will spread the torqued pressure of the bolt more evenly and flatly to the cylinder head. smile

As you torque the bolt without the washer the head will chew the aluminium a little and introduce indentations and gouges also. disbelief

These will flatten in time due to heat, expansion, contraction, etc and give more clearance to the bolt/head junction.

A thickish washer between bolt and head minimises these discrepancies. aww

Is it just one bolt or the lot? confuse

Either way, I would definitely use them to reduce any risk.

Your choice .......... blankstare
Martyn

fwtian · Veteran Member

damn.... I took the bike to a mechanic near me to torque the bolts cause i dont have a torque wrench....now i must do it again disbelief

2 washers are not in for sure!!!

Cubber · Super Guru

Why use a torque wrench?
The torque you need to be used can be worked out to foot pounds (ft/lb)
Measure the length of your spanner and pull the end with a spring balance or push it with the bathroom scales.
If the torque is 20 ft/lb and the spanner is 12 inches then push the end to show 20 lb on the scales.
Easy - once you have one done you can use the spanner exertion on that bolt as a guide for the others.
Martyn

colin13846 · Senior Member

Cubber wrote:
Why use a torque wrench?
The torque you need to be used can be worked out to foot pounds (ft/lb)
Measure the length of your spanner and pull the end with a spring balance or push it with the bathroom scales.
If the torque is 20 ft/lb and the spanner is 12 inches then push the end to show 20 lb on the scales.
Easy - once you have one done you can use the spanner exertion on that bolt as a guide for the others.
Martyn

I would personally just buy a torque wrench, far easier.

Just don't forget to wind it back to zero after using it

Cubber · Super Guru

I agree wholeheartedly Colin - and if a torque wrench is looked after and cared for it can be used time and again and last a long time.

As with all tools, however, I would advise shelling out on a good one in the first place. Pay cheap and buy twice. disbelief

If you are stuck for a special tool, though, then improvisation can get you out of a sticky position. aww

Martyn

fwtian · Veteran Member

i borrowed a torque wrench from a mechanic near me. But he had the big one for cars. So i used it only for the big bolts.

For the camshaft caps i will call a friend of mine who is experienced at bike repairs to show me how to torque them without a wrench ashamed ashamed !!! ( he works at a bikes workshop!!!!))

i hope i will finish today!!! biggrin biggrin

fwtian · Veteran Member

Pfiouuu... problem again!

i have the engine at I mark...

The problem is that i cant make the alignment markers to Align perfectly!!! :P

Cam lobs are pointing away from each other.

cam chain tensioner fitted.

Valve clearances are within specification!!!

Whats going on??? hmm confuse confuse confuse

TTRfan · Super Guru

Looks near enough to me!

A worn cam chain can sometimes allow a bit of "tolerance" on the cam sprocket marks cry

fwtian · Veteran Member

thanks Brian.

One more thing.

When i turn the engine with the wrench i hear a noise.... i think it comes from the starter motor but i am not sure.
Should it make noise? or when i turn the crankshaft there should be no noise at all?

TTRfan · Super Guru

If I recall correctly it sounds like it is turning the starter over in one direction (clockwise?) but is quiet going the other way.....

fwtian · Veteran Member

yes when i turn it clockwise i hear the sound! when i turn it the other way it is quiet! Is it normal?

TTRfan · Super Guru

fwtian wrote:
yes when i turn it clockwise i hear the sound! when i turn it the other way it is quiet! Is it normal?

I think so - anyone else know?

fwtian · Veteran Member

Brian can you please open the cap from one of your TTRs and turn the engine left and right??!!!!

i want to be sure that it is normal before starting my engine!!!

TTRfan · Super Guru

I just braved the cold and dark to go out into the garage and I am pleased to report that my memory was correct biggrin

Turning the engine clockwise is noisy as it is turning the starter over. Turning it the other way it is fine with no noise wink

fwtian · Veteran Member

Thanks a lot Brian!!! Tommorow morning i will fire it up!!! may god be with me :P

fwtian · Veteran Member

biggrin Bike started immediately!!! first starter motor spin !!!

it runs smoother than it used to run before the rebuild!

Now the problem!! evileye evileye evileye evileye

i cleaned the carburator...and now the choke is harder to pull and put it back.. ( i cant explain it better)

Also when i turn the throttle and leave it it delays. its like i leave the throttle and it works 1 more second like i have throttle opened before it stops.

( damn i must refresh my english disbelief )

TTRfan · Super Guru

Good news - glad to hear the engine rebuild was successful biggrin biggrin

When you rebuilt the carb, did you take out the choke? If a carb isn't used for a while it can gum up and get very stiff. Be careful as I used a bit more force on a stuck choke than I should have and broke the knob off disbelief

A bent choke rod can also cause problems. Take the choke out if you can (a description on how to do this is in an earlier thread) and give it a clean and a squirt of very light lubricant spray (such as WD40) before replacing it.

Regarding the slow throttle return, are the cables free and not binding? Unless there is some dirt on the throttle slide it is usually the cables that cause the problems. The throttle should snap shut when you let it go.

Brian

fwtian · Veteran Member

EDIT!

Everything works FINE!!! biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin biggrin

-- Edited by fwtian on Sunday 27th of November 2011 02:49:37 PM

fwtian · Veteran Member

Guyz my compression is 12,7:1 !!!!!! is this normal?? I know that stock compression must be 10,5:1 ...

i have OEM piston +1mm and i just had my valves cleaned, nothing else!

fwtian · Veteran Member

Today i checked my oil while the bike was running and i saw that the oil hasnt moved from the bottom of the engine!!! I turned it off immediately and i opened the check bolt to see if i have oil feed. Oil came out after 2 seconds.... I started the bike again with spark plug on and oil still doesnt move from the bottom!!! Yesterday when i checked the oil it was moving fine inside the engine, when the bike was running i couldnt see much oil from the glass.... but now it is full and doesnt move!!! Whats going onn???

TTRfan · Super Guru

Something going wrong I think - when the engine is running there should be enough oil circulating to take the level well down in the sight glass.

Did you do anything to the oil pump as part of the rebuild? Could the external oil feed pipes be loose or blocked?

fwtian · Veteran Member

no i didnt touch the oil pump... i change the washers from the back oil feed pipe because it was leaking.I put different ones.... but until yesterday it was ok...(it was still leaking a litlle with the new different washers.Could the leaking cause the oil no to move around the engine?)

i will put back the OEM ones to see if this is the problem...

It can also been blocked from the small piece of gasket glue that fell in during the rebuild... cry

-- Edited by fwtian on Saturday 3rd of December 2011 12:21:22 PM

TTRfan · Super Guru

Bad luck cry

Where did you need to use gasket glue?

It is good practice to use the sort of sealant that sort of dissolves in oil if it gets into the engine. I use some stuff in a red concertina squeezy type bottle - orang goo - can't remember its name but it saves having to worry about blockages... The only time I normally have to use it is when putting crankcases back together as they have no gasket.

I also use the equivalent of STP on bearings when doing a rebuild - just in case of problems - as this stuff really does protect bearing surfaces for quite a while until oil gets around.

Brian

fwtian · Veteran Member

the mechanic that i gave him the bike for the first service put black gasket glue on the cylinder head cover... When i opened the cover a piece fell in the cam chain space...someone from this forum told me to take it out... Some friend of mine said it will cause no problem.... i should have listened and take it out...

I want to believe that the different washers that i put are the problem... They are thinner so i put 2 of them...they are also smaller... they were a lot different...

the yamaha shop near me told me that he doesnt have this washers in stock... i will go at other dealers to find the oem ones....

fwtian · Veteran Member

something is going very wrong...i changed the washers but the oil still stays at the bottom... i opened my oil filter and i saw that it got really dirty with small metal pieces... the pieces must be because i opened the cylinder 0,5mm and the piston hasnt fitted yet !?!

fwtian · Veteran Member

Good News!!! i opened the clutch cover i cleaned everything, i open the oil pump and clean it too! i didnt see something that might have caused problem to the oil feed but when i started the bike the oil start to move!!! now almost all oil leaves from the glass and i can see it moving... i hope no damage to the piston/cylinder has been done... i am not going to open it... my heart will not withstand more damages! biggrin biggrin biggrin

TTRfan · Super Guru

Excellent biggrin biggrin biggrin

Does the engine sound OK and run without any smoke?

Brian

fwtian · Veteran Member

Before the rebuild i was hearing a loud tak tak tak tak!!! Now it is quiet...although i think that the exhaust makes more sound but it must be my imagination cause i wasnt riding the bike for 2 weeks... At low rpm there is no smoke! I will have to check at high rpm but not yet cause i have done only 60km!!!