I read all the hype about this conversion and everyone has put ther two cents in so I thought I would try it . First I started with the trx250r / 400ex a arms conversion . This adds about 2 inches to the front of your bike. The only problem I ran into is the bushings were a little wider than my 300ex bushings so I put my 300ex bushings in the 400ex a arms and that problem was solved . This puts your 300ex shocks in a bind so I bought a set of 400ex shocks on ebay . (450r ,ltz400 and the 450 yamaha shocks will work also ) But this makes the bike sit funny so I bought the shock conversion kit from ebay I think it was diamond j's which solved the problem . It has multiple settings for longer or shorter shocks and the quality seems to be great . It is a lot heavier than I thought it would be . I would hate to see how much their a arm kits would weigh . If I had it to do again I think I would buy the KOQ shock relocater kit from ebay it looks to be a lot lighter but It wont have the adjustability of the Diamond j's . Next came a complete 350x swing arm with the axle and wheel hubs I got a great deal on ebay $244.50 delivered to my door . The swing arm is maybe a little over 1 1/4 inches longer than a 300ex/250 swingarm. The 350x swingarm is 3/4 of an inch narrower at the pivot bolt but you can put washers to center it . If you use the 350x swingarm you will need a 350x shock . It bolts up to the frame nice but you need a new bushing for the top of the shock . The 300ex/ 250x uses a smaller bolt than the 350x . You can get brass bushings to fit it at Lowes or Home Depot but I had mine made at a tech school my son goes to . Next comes the 350x axle this thing is awesome it has larger splines than a 450r axle and is adjustable . The only problem is the sprocket hub is not as wide as a 300ex sprocket hub it's about 5/8 of an inch narrower so the sprockets dont line up . On another post someone mentioned having the sprocket hub pressed off and installing a 300ex sprocket hub . Everyone I have talked to says this is a bad Idea the Honda sprocket hub was not designed to come back off plus I can't find anyone who can do this . My son took an old 300ex axle that was no good to school and cut it down to fit in the press and could not get the hub off the axle . The hub crushed before it even started to move . I think they are heated to expand and then installed on the axle and when they cool they shrink back to size . So I dont think a 350x axle will work on my 300ex but if anyone else has an idea I would love to hear it . I a'm going to sell my 350x axle and buy a 300ex after market axle that is adjustable . So far I am very happy with how this is going I have'nt rode it yet because I a'm rebuilding my motor but I a'm very happy with how it looks . hope this helps someone doing the same project thanks

 

what brake lines and tie rods do you use with the 400ex arms? i just won a set off ebay thats going on my 250x but didn't know if the stock stuff would be long enough.

got any pics of your wheeler?

 

you can use your 300ex brakelines but you need to get 400ex tierods . you can use your tie rod ends you just need the longer rod . no pics yet I am sandblasting everything and getting ready to paint it . thanks Bob

 

I did the complete 350x conversion into a 300ex frame, engine and swingwarm, along with 250r/400ex shocks. Everything you said is pretty much correct. However i just kept the stock 350x axle in the 350x swingarm. Works just awesome. The Diamond J customs relocator is a bit on the heavy side but on the plus side it is really well built and looks good too. You are going to have to get the longer 400ex or 250r tie rods due to the wider a-arms. I replaced the stock brake lines with the stainless steel double lines. It eliminates the t-junction by the steering stem and I have noticed a lot more response in braking evenly on both tires. Hope to see some pictures when your done!

 

Did you have any trouble with your sprocket alignment? I have the whole rearend but when I install the swingarm I have 3/8 of an inch on either side . when I center the swingarm my chain doesnt run straight how about yours ? If it is straight did you modify something ? I dont think I want my chain to run at an angle but I would love to use the 350x axle . I also have done the 350x engine in a 250x frame about 15 years ago it was an awesome bike . I would like some more info on your swingarm and axle pics might help I am trying to get some of mine now . I am painting the frame , swingarm and a arms Mopar sublime green and my fenders a black I am going for a monster energy drink look . I have also made my own exhaust with a Honda 450r headpipe and muffler . I just cut the headpipe here and there and had a guy at work weld it up . I even used part of a 450r hrc pipe that is even bigger than a stock 450r pipe to make part of my headpipe fatter kinda like a FMF powerbomb . The whole thing only cost me about $60.00 not too bad and it looks really cool . Any help with the axle would greatly be appreciated I am getting ready to buy an extended 300ex axle if I cant get the 350x axle to work . But I would rather use the 350x axle thanks In advance . you can e-mail me at reevesbroswrestling@yahoo.com

 

All I did was make a spacer to fit the gap on the swing arm bolt ot move the keep the swing arm all the way to the left. It keeps the rear sprocket in line with the engine. However thats with the 350 engine in the frame. I would try to align the the chain and sprockets as straight as possible. Then try spacers on either side if you need them. Washers work great here because they are thin enough to to put several on either side to even it out. I'll try to get some pics posted a little later.

 

maybe the 350x engine is different but I couldnt get the 300ex sprockets to align so I used a aftermarket axle and its all good . I am getting spacers made at my sons tech school so I can center the swingarm . I hope to have my frame painted in a week or so and then I will post some pics . I tried to move my swingarm all the wat to the left side and the sprockets ligned up but the shock was kind of in a bind when I did that , plus I want it to run straight and not pull to one side or the other . My son put a 350x motor in a warrior frame it runs great . He used a 400ex carb with his and the 400ex headpipe which is a little bigger . I would rather have had it in a 300ex frame but he likes how the warrior is a little longer . He had to do a lot of fab work to get it in but it runs great and suprises alot of people who drag race him and think its a warrior motor . I bought a powroll 390 sleeve already pressed into the cylinder for a 350x on ebay for $50.00 only to find out they want $275.00 just for the piston when the whole 390 kit is only $315.00. Oh well you live and learn . Thanks for the advice

 

Udate on my project. Since my last post I have swapped my 300ex engine out for a stock 350x motor. It runs and handles great. I love the 350x swingarm . I get great holeshots with this setup . The bike sqauts and pulls the wheels about 10" off the ground for a few feet then it settles in and its gone . The shock and swingarm conversion makes it handle great . And the adjustability off the 350x rear shock is great . I will try to post some pics at some point . I am not too good with the computer.

 

hey guys also new here but hav been riding for years ... quick question, will a 350x swingarm just bolt into place?? also how much "stretch" will it add to my 300ex??

 

Yes it bolts into place but it takes a little work. You have to use some spacers and the 350x shock . It adds a little over an inch maybe an inch and a quarter . but it makes a bid difference in the way it handles . I like the way my rides now .