The Hodaka Club Forum

I have a 71 Rat motor and the left side case is pretty trashed..welded, broken etc...not a good candidate for a restoration...the right side case is ok...will a P or E series left side case be usable with the right side M?...I always thought the only difference on the bottom end of the rat and the ACE was the straight cut primaries and transmission gearing but want to verify..

Hmm, someone will come up with the answer, but a few weeks ago, I was checking crankcases for the new project. I had both engine cases in hand. The Rat case was noticeably heavier than the Ace. It has more base gasket area than the Ace. As I remember the Rat case pair was 3/4 # heavier. I'm guessing they're physically interchangeable but would certainly look weird around the base gasket area!

Max

If you needed a case contact Diane at California Hodaka, [email protected] They are well stocked in good used parts, and if they have it they will fully check and clean it to make sure the part is very usable. They also have new parts as well and can service and machine parts also. They don't have a web site, but are one of the best, as well as Hodaka Dave, and Terry Larson at Hodaka Parts.

I have checked two Rat motors and neither had cases that would mate with the P or E series engines. The locating dowels were larger on the Rat motors I had. I am not sure if this applies to all of the 93 Rat motors or not.

Brian

When I was building my Rat, I noticed a couple things concerning the M-series engines. My Rat was a very early model 93, built in Oct 1969. It's engine had a left side that was trashed and like you, I thought I could just swap out a standard 100cc left side. Not so...

While looking for a replacement, I noticed that the early P or E series engines had a thin cylinder deck as Max indicated. Even though they would mate up OK, the size of the cylinder deck was a problem as my Engine had a very large or wide cylinder deck.

I did find some P series engines with a large deck. I think these may have come from a (96) Dirt Squirt, but cannot confirm. But then I noticed another problem...

The Chrome tank Super Rat M engines used bearings instead of bushings. Where the P series engines used bushings for the Main shaft and counter shaft, the M series engines used needle bearings. But this is an internal issue and may not even matter since the shafts will still work fine with bushings. Or.. you could have the bosses reamed out for the bearings.

I know it doesn't really answer your questions, but thought I would save some research time and share what I found out. I ended up taking my case to a very competent welder here and he repaired my case. His repair was undetectable when he finished and only cost me about $100. A bargain, since I couldn't replace it.

$0.02

Roger

My understanding is that all of the early 100 cases had the smaller cylinder deck size...both the Ace's and the Super Rats. The deck size increased when Hodaka began to make 125's, as the same engine cases were used, just certain areas were machined differently (mostly the area where the cylinder spigot fits into the cases). As far as the Super Rats having needle bearings and they Ace having bushings, that is correct, but either will work fine, the transmission shafts are the exact same size.

My foggy memory is that rat engines ENGINES had needle bearings and some had bushings. Also early rat engines had the narrow deck. ---------------Clarence