DS7 case vs. R5 ?

[soonerbillz]

So my R5 project has only a DS7 lower unit in it. No top end.
I want to build a 6 speed motor and put 350 top end on it.
I have read many of the posts about doing the rd400 trans and clutch swap
Not certain yet whether to search out piston port or reed jugs.  The bike will see a mix of country back roads and highway use.
My main question right now is whether the DS7 bottom end is a worthy one to build from or should I just find  R5 unit..
Is one any better than the other for this project. ?

[m in sc]

r5 and ds7 cases are the same, so no matter there. however, the 250 (ds7) has a different primary gearing than 350 units. so, if you ant to change out the clutch, etc, you should probably go for a 350 or 400 primary gear/clutch setup.  r5 and ds7 cranks are interchangeable as an fyi.

[AAAltered]

To add to what mark said:
- R5 jugs, pistons and carbs are unique to that top end.  Some of the specifics are 5 port cylinders, oil injection into the cylinders, no reed blocks, manifolds/ spigots for the VM28's, specific carbs,  specific pistons for the 5 port, specific base gaskets for the 5 ports.
- RD jugs, carbs and pistons are unique to THAT top end. 7 port cylinders, reed block manifolds for the VM's,   Specific Carbs have the oil injection port instead of the cylinder, specific pistons for the 7 ports, specific base gaskets for the 7 ports.

Without debating one top end over the other, some like the wild hit of the 5 port setup over the supposedly smoother power deliver from reeds.

My point is when you decide a direction, make sure you stick to it when acquiring the top end parts.

Meanwhile, lots of other stuff DOES interchange between those two setups, like heads, small end bearings, clips, and wrist pins, etcs.

When you choose your direction you will see all of this as you seek parts for the build.

Good luck, we've been there.

Here is some inspiration....

Day One, rescued from a basement after 27 years sitting (ps it didn't run...):



Many Days After:

[Jspooner]

Doing the swap(s) you mention is not difficult, it is all remove and replace stuff but you need to make sure you have all of the right parts when doing so. If I were you I would forget about the trans swap and rebuild the bottom end you have and use it. If you want a 350 just look for an R5 top end to put on it.

[soonerbillz]

Doing the swap(s) you mention is not difficult, it is all remove and replace stuff but you need to make sure you have all of the right parts when doing so. If I were you I would forget about the trans swap and rebuild the bottom end you have and use it. If you want a 350 just look for an R5 top end to put on it.

Why would you not do the trans swap?

[soonerbillz]

Thanks to ya'll for responding.
Decisions...decisions...

[Jspooner]

Thanks to ya'll for responding.
Decisions...decisions...

I guess it really depends on how you are building the engine. I have ridden a mildly modified R5 with the stock trans and it actually worked pretty good. If you are convinced you need an RD trans just look for an RD350 bottom end. You will need a lot of the parts from it or just use it.

[bhh1989]

Thanks to ya'll for responding.
Decisions...decisions...

I guess it really depends on how you are building the engine. I have ridden a mildly modified R5 with the stock trans and it actually worked pretty good. If you are convinced you need an RD trans just look for an RD350 bottom end. You will need a lot of the parts from it or just use it.

What about the jump from R5/DS7 tranny to RD400 - is that worth the hassle for your average moderate build?

[Jspooner]

I'm still not sure I'd do it. Maybe if you're a really aggressive rider and always on the pipe and ride like Ricky road racer then yeah, you might want to do it.

[EE]

As a general rule i'd say always update to a 6 speed if your going to be riding it. If you can. And update to the RD400 trans if your going to build the engine pretty hot and ride hard or race, If not stick with the 250/350 6 speed from my experience of rebuilding just piles of trannies.. it's alot easier to find parts and in better condition for the 250/350 6 speeds but for racing....the 400 trans.
I think the DS7/R5 cases used only the half case bearing retainer on the input shaft clutch support bearing.
And DS7/R5, RD, and LC 259/350 base gaskets all interchange.
If you swap for either 6 speed you'll need the 6 speed shift drum and shift forks too but that's it!

[soonerbillz]

As my update my build thread indicates.. I am doing the 6 speed swap. Also the late RD350 7 disc clutch.
Will I need a different tach gear when putting the RD trans into my yds7 lower end.

[Jspooner]

As my update my build thread indicates.. I am doing the 6 speed swap. Also the late RD350 7 disc clutch.
Will I need a different tach gear when putting the RD trans into my yds7 lower end.

Yes, you'll need the tach gear from a 350. Your tach will work either way but it will be even less accurate if you don't swap the tach gear. Also, I'm sure you figured this out but you'll also need the primary drive gear for the crank to go along with your 350 clutch.

[soonerbillz]

As my update my build thread indicates.. I am doing the 6 speed swap. Also the late RD350 7 disc clutch.
Will I need a different tach gear when putting the RD trans into my yds7 lower end.

Yes, you'll need the tach gear from a 350. Your tach will work either way but it will be even less accurate if you don't swap the tach gear. Also, I'm sure you figured this out but you'll also need the primary drive gear for the crank to go along with your 350 clutch.

Thank you. Yes I have the primary gear.
Attached is a pic of the RD350 trans set I purchased from another member of the board.. I think minus the tach drive this should be all I need for the swap.

[soonerbillz]

I'm going to replace all the bearings with new ones.. the gears all look good.. not a lot of wear and no chips, broken teeth. the forks have some shine wear on them but still plenty of life left.
I'm also going to have the yds7 crank rebuilt..