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

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: XT 350 Top End


Senior Member

Status: Offline
Posts: 107
Date:
XT 350 Top End
Permalink  
 


Long story short, my 1993 TTR 250 had sprung an oil leak, it was oozing for ages, then suddenly something must have given way because I got home from a ride and oil was pouring from around the base gasket.

I proceeded to order a head and base gasket set. While changing the gaskets, I noticed the piston was ruined, well maybe not, but why not do it while in there? I then ordered the Wossner 263 piston kit from Brian here. I rebuilt the whole top end eventually and changed every gasket in that engine in the end. I could strip that engine with my eyes closed now. So, I had the bike rebored. Boy, did that piston make a difference. I can't tell if it is because I actually have some compression now, but it certainly gave the bike that pep I was looking for. I have done 2000KM's on that piston now. Seems to be going well. The bike no longer sounds like a lawn mower, so there's something.

Here's something I considered, while looking for parts that would fit my bike, whilst being cheaper, I noticed lots of XT350 engine parts looked very similar, I even have some gaskets and some other stuff off a 350 in my bike now. I was wondering if anyone has ever tried to fit the top end off an XT onto a TTR? The parts fisches make the engines look very similar, and I was wondering if it would make a cheaper option than the 325 American kit?

Adam



__________________

Adam. 1993 Open Enduro: 14/48 Gearing, Uncorked, Twin-Air Filter, Snorkel Removed, 263cc Piston, Ported and Polished Head, Shorty Header, DG-O Silencer(Loudener!), 140 Mikuni Main, Standard Pilot, Bottom Needle Clip (Still A Touch Lean)



Senior Member

Status: Offline
Posts: 116
Date:
Permalink  
 

I just checked the specs and it seems like both motors have the same stroke. I suppose the rest will be up to cam chain alignment.

__________________


Super Guru

Status: Offline
Posts: 1481
Date:
Permalink  
 

the 350 top.end fitted straight on early tt250s untill a change of the stud pattern .which as far as Iknow continued on with the ttr 250 .



__________________


Senior Member

Status: Offline
Posts: 107
Date:
Permalink  
 

I thought maybe the studs may not align fully. I also considered the difference in cylinder-head design. Could lead to problems, or maybe the need to fabricate an engine mount.


http://pdn1.vnexttech.com/yam/mcy/1988/xt350u_uc/cylinder/assembly_files/11/1_1.png

http://pdn1.vnexttech.com/yam/mcy/2000/ttr250m_mc/cylinder_head/assembly_files/10/1_1.png

They are very similar. I think if the gudgeon pin fit the piston, which I suppose it would, and the piston could pass through the crankcase unrestricted, I don't see why it couldn't be made to fit.

You would also need to consider the twin header pipe design of the 350. If I could ever pick up an old 350 for cheap, even not running, I would like to give it a go.



-- Edited by Fladdem on Tuesday 4th of March 2014 09:29:42 PM

__________________

Adam. 1993 Open Enduro: 14/48 Gearing, Uncorked, Twin-Air Filter, Snorkel Removed, 263cc Piston, Ported and Polished Head, Shorty Header, DG-O Silencer(Loudener!), 140 Mikuni Main, Standard Pilot, Bottom Needle Clip (Still A Touch Lean)



Member

Status: Offline
Posts: 23
Date:
Permalink  
 

ttboof wrote:

the 350 top.end fitted straight on early tt250s untill a change of the stud pattern .which as far as Iknow continued on with the ttr 250 .


 Mmmmmmm Having an early RAID that sounds interesting, I assume that the valves on the 350 heads are bigger?

It'll need to wait till I've sorted some bigger valve heads for my monster unless one happens to crop up in the mean time.



__________________


Veteran Member

Status: Offline
Posts: 54
Date:
Permalink  
 

Anyone ever confirm the viability of a top end swap?

__________________
Moo


Senior Member

Status: Offline
Posts: 389
Date:
Permalink  
 

I very much doubt it would fit, otherwise the other guys would have gone to the trouble of casting a new 350 barrel



__________________


Super Guru

Status: Offline
Posts: 1481
Date:
Permalink  
 

Not ttr 

But my TT 250 cracked between the spark plug and exhaust valves . a srx 250 road bike head went straight on slightly higher compression a bit better down low grunt 



__________________


Super Guru

Status: Offline
Posts: 1378
Date:
Permalink  
 

I considered this early on to achieve the e start 350. TTR250 crankcases have a different bolt pattern and the mating surface for the bottom gasket is not the right shape. Other differences: gudgeon pins are different, conrod is different length... I even thought about filling the barrel/head bolt holes and building up the base gasket surface with ally weld then machining to suit the old 350 barrel, then you have to sort out cam chain length and timing, try and fit 2 carbs where there's barely room for 1, make up exhaust mods etc... Sorry folks, there's no easy way
Ride safe, and dream,
Simon.

__________________


Veteran Member

Status: Offline
Posts: 54
Date:
Permalink  
 

Sounds like a fun project..

 

I wouldn't run two carbs, I'd machine an adapter and run a single larger bore carb.  Timing.. an adjustable Cam sprocket set could easily be used/made to since timing for chain length..

How about the 350 head on the stock jug with a 325 kit?  Would give you bigger ports, valves and better suited camshafts!  Probably would be allot easier to machine the head for offset bolts than the case...?

 

Fun to internet engineer..hahaha

 

Chris



__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard