UK 300sx pics

[Jason T]

My dad has wanted a 250sx for ages now, and after some searching and waiting we found one, the bike was in good condition, but it was located in Germany and didn't have an engine!! So after a 1200 mile journey we got it home, stripped it down and got it ready for a new engine, that all happened about a year ago.
We had heard some people on here talking about fitting a 2WD TRX 300 engine in an SX, so we thought why not give it a go. We located a complete 300 engine, and then checked that the engine mounting holes would line up with the frame holes.
When we had confirmed this we set about rebuilding the engine, which was in worse condition than we expected. In the end it needed a rebore, new piston, cam, rockers, one way clutch and a starter motor. I finally got around to assembling it last week, which went well, until we realised some of the wiring on the 300 engine is different. It was decided we could overcome this problem so I started to mount the engine in the frame, which is when I found the major problem!!!! The angle drive for the shaft on the 300 engine is about half an inch further across than the drive shaft on the 250 frame (see pic) :cry:
We are going to have to swap to a spare 250 sx angle drive we have, the bad news is that the angle drive incorporates the shaft that most of the gears in the gearbox are mounted on, so to change it I have to strip the engine to every last nut and bolt!!!!!!!!!!!!!!!!!!!!! :mad:
For the moment it has been pushed to one side in the shed, but we have spent tooooo much money to give up on it. So keep your eyes peeled for an update on progress in the near future :TrikesOwn

Jason T

[Maine_Triker]

It's too bad that it didn't work out the first try. But when you get her all together, that's going to be an awesome trike!!!! GOOD JOB!!!

[RCGUY]

one of my friends is doing that swap but to a bigred . you don't have to strip the motor all you have to do is put the motor on its side on bolt the 300 angle drive and take it out VERY carefully and then slide the sx one in VERY carefully bolt it up then you done that part , next you have to take the clutch cover off and then you will see that the oil feed tube that runs in to the shaft needs to be bent a little bit atfter that put it all back together and your good to go

[Dirtcrasher]

RC is correct, the gears themselves line up fairly easy. The problem is a thrust washer which I believe is next to first gear that falls down when you slide out the shaft. But even if that happens you can get in there and get it back in position without splitting the cases.

[Jason T]

We thougt it could probably be done, but like dirtcrasher says its a bit risky with the thrust washer :wondering
I guess we will give it a go, hopefully soon, I'll keep ypu updated :TrikesOwn

Jason T

[Dirtcrasher]

We thougt it could probably be done, but like dirtcrasher says its a bit risky with the thrust washer :wondering
I guess we will give it a go, hopefully soon, I'll keep ypu updated :TrikesOwn

Jason T


Remove the clutch cover, kickstarter gears and kickstart idle gear which also has a small collar behind it. Then lay it on the side as RC suggested and when you tip it back up after the swap you can see right inside the case and verify that the all important thrust washer is in place.

Also be aware of what gears have washers and spacers on that countershaft. From the SX to the ES I have seen a couple of different setups.

Please let us know if that fixes your alignment problem as some of us may want to do that same swap.

And I also wondered what the electrical problems were that you ran into??

[Jason T]

Made some progress on the 300sx! We took the advice given in the thread and partly stripped the engine down (pic 1). Then we tipped the engine on it side and I fed a piece of tube up as my dad pulled the angle drive out, to make sure everthing stayed where it should! (pic 2) I hope you appreciate that pic as my dad was annoyed I was taking pics at such a stressfull moment!! :eek:
The next pic shows the SX angle drive next to the 300 one, the gear and clip that are on the bench were taken off the 250sx shaft. These were removed as the 300 gearbox doesn't use a clip on this gear.
continued below..............

[Jason T]

The first pic here shows the diference in the oil feed holes in the ends of the shafts, the larger one is the 300 one. As this is just a cap in the end of a hollow shaft we drilled the 250 one out to the larger size.
The next pic shows the difference in the ends of the shafts, the longer one is the 250. This is why, as RCGUY says, the oil feed pipe needs to be bent up a bit, even with the pipe bent up it still clears the clutch fine ;)
The final difference can be seen in this pic as well, the 250 shaft has a small hole near the end, but the 300 doesn't. So no oil drained out of this hole we filled it in with some JB weld, it may not have made any difference, but we know for sure it won't now :D
The last picture is the engine put back together and in the frame with the carb and airbox on. The 300 carb is a tight squeeeze but fits okay, the throttle cable is going to be a bit of a challenge though!!
After all that I can say that the 300 engine will fit with the 250sx angle drive, with just the end of the shaft to drill and a slight adjustment to the oil feed pipe :TrikesOwn

Jason T

[Jason T]

The electrical problem that I mentioned is that the 300 engine has a different amount of wires coming out of the stator, and that the 300 engine only has 1 wire going to the pulse generator, while the 250 engine has 2 :wondering
Not sure how we are going to solve that one, any ideas?

Jason T

[ATC crazy]

Wow...a 300SX...thats amazing!
I was wondering if you couldnt modify the engine mounts to slide the whole engine over 1/2" or so.

But it looks like ya'll have solved the problem already. Congrats!

[Dirtcrasher]

The electrical problem that I mentioned is that the 300 engine has a different amount of wires coming out of the stator, and that the 300 engine only has 1 wire going to the pulse generator, while the 250 engine has 2 :wondering
Not sure how we are going to solve that one, any ideas?

Jason T


So the output shaft allowed it to line up perfect? Or what??

Grab urself the wiring diagrams and that should help. Maybe the SX had a dedicated ground and the 300 had a common ground.

I give you guys lots of credit for attempting this swap. Most people would chicken out...

That hole in the shaft I believe is for splash oil through a couple of holes in the splined shaft. More important is the pressurized hole that feeds that right angle drive. There is an o ring out there that needs to be in place so just confirm all that stuff is AOK. Good luck!

[Jason T]

Yes, to clear it up, using the 250sx angle drive allowed the engine to line up perfectly with the drive shaft and the engine mounts :TrikesOwn

Don't worry we remembered to put that little o-ring back in ;)

We're working on the wiring problem, when we've found a solution i will post an update, and hopefully a ride report as well :w00t: We've got the honda manuals for the 250sx and the trx 300 so that should help us a bit ;)

Jason T

[Howard]

I would like to know how this is still working? everything still running good? hows the power feel compared. is the swap worth it? cost efective? let me know.

Thanks, Howard

[BigGreenMachine]

Pretty sure fourstroketech.net makes a 425 cc bigbore for the 300 honda utility bike so that could be one potent trike.

[Jason T]

Hi Howard,
The 300 is running really well;)
The best comparison would be with our 250es, and it does go a lot better than that. Where it is a lot better is in deep mud, it will pull a higher gear than the ES with no problems.
As to wheather it is worth it or cost effective depends on if you can get an engine cheaply.
Our engine needed a lot of work to get it up to standard (New piston, bore, cam rockers, both clutches etc)
But if you can find a good 300 engine fairly cheaply it would make it a better option.
I would say you can come and have a go on it, but its a bit of a trip:eek:
If you read some of my other threads on it you'll see we had a bit of a problem with the wiring and a few other things, but if you don't mind a bit of work it makes for a very good conversion.;)

Jason T