Hi, i am interested in buying an FZR250 in the EU and i am collecting data at the moment. It will be my first yamaha and i am looking into the interchangeability of engine parts between years of build, because the stuff is quite rare... I hope some of you guys riding the amazing little bike can help me with some details. Are the earlier engines different? Or are they only different in single and specific parts? According to the parts catalogue they handle the engines seperate, but parts number sometimes are equal except of the prefix. How specific is the prefix? Did they completely rework the engine? Does a workshop list exist of interchangeable parts? Is it correct that the best identification mark between pre and post 88 are the additional mountings in the cylinder head for the aluminium frame? thank you very much with your help with this beginner questions regards, spark
My knowledge is a drop in the bucket compared to what's here but I'll start. The steel frame (2KR) engines will only fit in 2KR frames because no mounting holes in the head. These engines have 4mm valve stems and slightly different crank conrod piston sizes. The 3LN aluminium framed motors will fit in the 2KR frames and have 3.5mm valve stems and the different crank conrod pistons. The bores and stroke are the same, just the length of the conrod changes. I think there's a few little things like oil squirters in the later engines too. Sent from my SM-G991B using Tapatalk
Hello and welcome to the forum Adding to what @neoncrypnid said. On part numbers the prefix and suffix can both be important - you will have noticed that many 3LN parts are 1HX prefix for example. In some cases the suffix will denote a different size/colour of a part, engine bearing shells for example. On a basic level almost every thing will fit with almost everything with some caveats. Cylinder heads are interchangeable between engines noting the difference/lack of mounting bolt points on the 2KR cylinder heads which related mounting in the frames. The 3LN1 service supplement in the resources section, although in Japanese is informative as that's the point of many engine related changes, crankshaft, conrods, pistons and camshafts. Yamaha resources section: https://www.2fiftycc.com/index.php?resources/categories/yamaha.11/ Barrels are interchangeable because bore remained the same. Crankshafts are interchangeable because stroke remained the same BUT the taper on the crankshaft where the flywheel fits is different between 2KR and 3LN. 3LN crankshaft is lighter I believe because the FZR250 engine development closely mirrored the FZR400. Conrods and pistons are matched between 2KR - 80mm conrod and piston compression height to match, 3LN 82mm conrod and piston compression height to match - check the 3LN1 service supplement. Camshafts are interchangable, BUT there are differences in duration and timing between 2KR -> 3LN1/3/5 and then change again to 3LN6/7 which have reduced power output. Valve stems changed from 4mm [2KR] to 3.5mm on the 3LN models. The Zeal 250 is a slightly detuned 3LN engine, 3.5mm valve stems, different camshafts [timing and duration], no EXUP and slightly smaller carburetors . There is a steel framed model with the EXUP valve which sits between 2KR and 3LN - some details here https://www.2fiftycc.com/index.php?threads/fzr250-model-descriptions-and-identification.6668/ Also those frame numbers will assist in knowing which model & year it was manufactured which can be important for engine and other details. hope this helps
Wow, thank you for the detailled informations, this is more than i expected! I will carefully choose the type of engine i need. hopefully the different parts are marked in a way to be unique. Many people refer to the fzr400 in terms of service manuals as the maintenance and service operations are similar. Other users reported to successfully put a fzr250 engine into a fzr400 frame. I guess it is needed to divide also between frame revisions. But will the 250ccm 2KR to the 400ccm steel frame and 250ccm 3ln to the 400ccm alu frame? Are there any limitations? /not to downgrade a fzr400 but maybe in terms of engine testing in a chassis. Thank you for your help, i will also refer to the jp manuals. Maybe i find a online translation service. I tested the google service for single pictures and... wow!
The engine cases have the same mounts points between them across the range, there is the difference with the cylinder head mount bolts from 3LN onwards. The same change occurred on the FZR400, it went from an engine cradle on the 1WG to a fully stressed member with the cylinder head mount points for 3EN [UK model] 3TJ [Japanese model]. You'll like the information on this page http://my-x15.net/FZR_INFO.html The service manuals are formatted in a very similar fashion, the preference for the FZR400 service manual is because it's in English, editions of the FZR250 service manuals are only in Japanese. You can cross reference between the FZR400 and FZR250 manuals. I would consider an FZR400 frame with the 250cc engine might be underwhelming, going the other direction with the FZR400 engine in the 250 frame would be interesting, BUT the mount points in the cases are differently spaced. I'm sure something could be fabricated to mount the 400 engine [FZR600 and YZF600 engine mount points are the same as the FZR400] into the 250 frame - I was thinking of doing that myself at one point.
Do you think that (across models) equal parts parts have equal parts numbers? Therefore the idea would be to cross reference fzr250 to fzr400 on equal parts. Based on parts lists. The design based on exploded parts structure is expected to be equal. Does somebody own a fzr400 parts catalogue to provide?
https://drive.google.com/file/d/1IsPjSMSmE9CbVp1k2gIegV5N-ljTuVez/view?usp=sharing https://drive.google.com/file/d/1ZbfLYZ9r3Xl7bqGPgZqX6Cn9CckPldqD/view?usp=sharing https://drive.google.com/file/d/16cD0i6fFQbODU6eDSzqf2k9i2xKmjj0Q/view?usp=sharing https://drive.google.com/file/d/1qwACfYjgAY8dZlA5Ya9vAqCtXWMVX8K3/view?usp=sharing
