1968 Yamaha DT1 Treasure/Trash?

YES! Also consider deraking the steering head. I have a frame for rebuilding my crashed TT500 that the steering head is pulled back to 23 degrees. It may be a little steep for but it will handle a bunch better!

I was eyeballing my bike last night, and this is some thought I was/am having.

If I lower the bike about three inches with suspension mods, my axle centerlines and crankchaft centerlines will be near even (a good thing, to create neutral leaning in the corners), I will have a lower seat height (a plus), shorter shocks, and have a similar swingarm angle as the cradle drop mod.

But, if I drop the cradle about two inches, and I get creative with it, I could gain room where the air filter goes through the rear down tube (a plus). I would have near stock shock and fork length. I would have more suspension travel area (which I won't need for flat track only). And, it seems as if the center of gravity would be higher than a suspension drop.

I am just thinking out loud here. My ol' school Yamaha mechanic buddy doesn't think I should cut up such a nice (titled) bike. To me, it doesn't much matter. It is going to be a race bike, not a trailer queen.

I think you're on the right track lowering the frame 2 inches will lower the center of gravity. what you want is a swingarm angle positive about 7 to 10 degrees. The steering head pulled back will help it into the corners and that should solve most of the problems with what you're working with.I have an RT2 frame I believe that's what it is if you want to chop one up

Here are some more idears;

If I were to drop the cradle two inches, the axle center lines would be about an inch below the crankshaft center line. Have all three lined up creates neutral handling in the corners. So, the one inch difference still has the bike having a top heavy characteristic (bad). You still get to keep stock length forks and shocks. But, the swing arm is going to have a near flat angle (not ideal, but not bad). The bike still has a tallish seat height (not ideal). And, the bike still has stock suspension area (not really needed in flat track). Dropping the cradle also lengthens the wheelbase slightly, and transfers a little more more weight to the rear (good for traction). Ideal wheelbase is around 54 inches, which is near stock. I have read that a swing arm extension kit was also available, and complimented the cradle drop kit. At that point, the wheelbase would be to long, so de-raking the neck would be next up. De-raking the sock 29* or so angle to about 26* would be great for short track, not as good for half mile.

Ok, how about keeping the frame stock? Drop the suspension the three inches that I mentioned before. Install shorter shocks in the rear. Slide the forks up, or install shorter ones up front. Keep in mind, you probably would not run the junk stock shocks anyways, so getting new short ones probably would not have a cost difference. Same with the forks, you would probably at least rebuild the stock forks. Now, you have a neutral handling bike, lower seat height, and no welding or machine work to do or pay for. The swing arm angle will be near flat, like the cradle drop mod. Want to de-rake the neck angle? Sure, no problem. Slide the forks up in the triples, and install longer rear shocks. The neck angle has been reduced for quicker steering, and you installed a set of near stock length shocks in the rear. With the suspension drop, you probably lost a little bit of wheelbase. Want to fix that? Install a set of triple clamps with more offset. You probably would not want to just the stock iron clamps anyways, so cost difference is near nothing. Not only does that lengthen the wheelbase back out, it also makes the engine think that it is closer to the rear wheel, and traction increases.

Like I said, I am just practicing years of research from real world results. I have not personally track tested these ideas, yet. But, I did use these ideas while building my TT500 flat tracker.

sounds like you have the experience to do this Justin. main thing is that you want about seven degrees positive swingarm angle.you mentioned that you had some experience with a TT500. just apply all that to your current project. Your head angle is going to be B your preference whatever you're going to ride short track or half mile the angles going to be different.You can't set it up perfectly for both so just find a nice compromise. Good luck.

You guys win No can do...

What do you mean?? Anything is possible! Different forks and a 19" front wheel to start with.
It gets easier from the point you're at!!
I have a none titled frame if you want to cut on one for your project.

The tire in the photo is 27" tall, same as the DT IIs I will be using. I cut my frame up yesterday. I am looking for tubes to throw into my lathe and make my extensions.

Seemed like a good idear...

I added 2" to the frame. Using 14" shocks I get a slight rake in the frame, 24* in the neck, and only 4* in the arm...

That's looking great!
Keep the posts comin.
I want to see where you go with this.

I am waiting on a YZ360/TT500 rear wheel/hub that I ordered. I wanted to get away from the cush drive hub. I may shorten the rear sub frame a few inches, or even cut them off. I am going for a Trackmaster look. I am having the stock tank fixed, and will have it painted pearl white. I am not sure if I will use Dunlop K70 or modern Goodyear/Dunlop DT tires. If you click on the link below, I have a build thread started on the new Yamaha Enduros forum.

Parts for sale; This bike was bought to race and the owner had the dealer install a big bore racing kit first thing. The original cylinder, head and various other OEM parts were taken off and replaced by afttermarket stuff and the original parts have been sitting in a box in a garage for 45 years and are now offered for sale ---best acceptable offer--individually or for the whole package! I'd think they would be of value to anyone restoring to original spec? I'll have a photo of the parts available to anyone with interest--- (I'm old and don't get on this site except every once in a while so it would be a good idea to email me to get my attention----lynnandnancy@gmail.com)

Deseret Rider, you might want to put this info in "Flea Market" for more views and people interested.
Just a suggestion