Cylinder To Base Dowel Pin Missing Ok To Run?

[JordanYZ80]

Hi there just rebuilt my bike with only one of the two dowel pins in place its a YZ250 2003 bike runs and sounds fine would i be able to hear if it was mis aligned or something like that and is it safe to keep running, thanks guys

[numroe]

Do you mean the cylindrical locators around the bolt studs on one side?

 

I wouldn't run my motor without both locators installed. Not for long anyway.  The cylinder could/would eventually rotate and cause an air leak or maybe cause early wear to the piston or a rod end.

[William1]

No

Install the dowel They are critical.

[yz250474]

I wouldn't run it, they are only like $5

[JordanYZ80]

Yeah thats the ones there should be two but i only have one installed at the minute, as said it runs and runs well just waiting on the other dowel to get delivered, did want to go out on it today but if its going to be a problem i will leave it. Wasnt sure how crucial it would be.

Thanks.

[arnego2]

at 30nm per nut the chances to have a cylinder roll on its base are slim at best. Specially as the piston action is not really turning but a stiff up and down.  

Being Yamaha sure you cannot. And in the end there is always a rest risk. So its up to you ?  

[JordanYZ80]

at 30nm per nut the chances to have a cylinder roll on its base are slim at best. Specially as the piston action is not really turning but a stiff up and down.

Being Yamaha sure you cannot. And in the end there is always a rest risk. So its up to you ?

Cheers buddy good answer, dont forget about the cylinder head mount that is clamped to the chassis also that mount is on there really tight also isn't it.

[JordanYZ80]

But I suppose its also i case of making sure its clamped 100% central in the first place isn't it

[numroe]

Cheers buddy good answer, dont forget about the cylinder head mount that is clamped to the chassis also that mount is on there really tight also isn't it.

The frame isn't solid. It bends when you ride. Even more so with the steel 03 frame.  So twisting forces going through the cylinder head mount are probably more likely to rotate the cylinder on the cases. If you really want to ride with with just the one locator installed then probably much better with the head mount removed and just take it easy.

 

Consider the head to frame mount being there to support the frame, not the other way around.

Edited June 21, 2016 by numroe

[YZDOC]

I wouldn't run without. But then again, I wouldn't even assemble until I had the part to install. Your choice may very, and the results of that choice may, or may not be detrimental.

Just my personal professional opinion.

[turbo dan]

I've run motors missing one dowel in the cylinder base.  If you're a little off it might be down a little on power if theres a big enough mismatch between the transfer port casting in the cases VS the base gasket and cylinder.  I don't think you could get it far off enough to cause mechanical issues.  The base studs will only allow so much movement in any direction.

 

If it put together and running fine I would certainly not take it apart just for that.  Just have a dowel ready for next time. 

[desrider891]

Too cheap of a part to leave out

[Aive1]

my 125 03 was running fine without both dowel pins, without cylinder head mounts; with a melted plastic on crank halves and cheap ims taiwan rod (I don't even want to imagine who and how rebuilt that crank)...a little bit rich but ok

[YZDOC]

Hmm, I have an IMS rod kit and it's made in the USA. Strange that yours is Taiwan. Your Taiwan one could be during transition when Hotrods bought IMS out I guess. Go figure... Hotrods.

[Spooge]

Um yeah don't

 

The number one rule to doing your own mechanical work is:  1.  Stop when you don't know what you're doing and get some help.

                                                                    Rule number two:  2.  Those Japanese engineers are pretty dang smart, if they put it there, they did so for a good reason.