[ds1506]

Hello everybody,

I've got my eyes on a kinda crusty XL100 that's for sale for pretty cheap near me right now. It's a 1976 with the twin shock and the double down tubes. Owner says it needs work, but I'm not sure how bad it actually is yet. I also happen to have a 1997 XR100 around my house and I was wondering, will that engine swap right in without having to modify the XL frame? Judging by pictures, the motor mounts look similar, but I wanted to find out if anybody knew for sure before I dropped the cash on it.

I've been kicking around getting the XR street legal for short distance trips and all, but if the XR engine will swap right into the XL, that would save me from a lot of paperwork and waiting to get my dirt bike street legalized.

 

[Larkin Nick]

Did you find out if this swap works? I am in a similar situation and wondering if the swap works before I buy a newer xr100 with CDI to replace my older xr100 points ignition motor.

 

[fatcaaat]

i just put an xr200 engine into a 1978 xl125 frame. I had to trim a slight amount of the frame between the back engine mount points but everything else fit nice. I do think that the 76 is different. The engines for the 78 and foward are much more similiar i think.

 

[Larkin Nick]

That sounds like a fun bike.

 

[T Bolt USA]

its my understanding all xr75 xr80 and xr100 are the same main motor mount bolt pattern

 

[fatcaaat]

its my understanding all xr75 xr80 and xr100 are the same main motor mount bolt pattern

Bolt patterns, yes, but they are not always the same on the top. Wider cylinders, different heads, in some cases different clutch covers. Really the bolt pattern is the same for xr75, xr80, xr100/crf100, 125, 150 xr200 and crf230. It's the top mount and clearance you need to be aware of.

I'd bet for certain that an xr100 motor will fit inside the older frame. An xr200 will likely fit too with some trimming. For me to put the xr200 in the 1978 frame, it took about 3 minutes with my die grinder to make clearance for the clutch cover but otherwise mounted straight in and I was also able to reuse the front mounts without modification.

 

[ds1506]

Ok, I guess from what I've learned over the last few years is that the pre-1978 XL100s were the same engine family as the CB/CL/XL 125. So the 125/185/200 (the 150F and 230 engines too, theoretically) Honda engines as well as the Chinese air cooled honda clones (up to 250cc) all fit.

The post-78 XL frames are closer to the XR100, so XR/XL 75/80/100 should fit those. There are a few images/videos/references to 200 engines being crammed into this type of frame, but I'm not sure how much work it'll take.

 

[Larkin Nick]

I have been slowly accruing parts and am finally getting started on the swap. It wasn't my post originally but thanks for all the advice!

So far I have purchased a 2001 xr100r with a tb120 kit that I will be taking the motor out of to put in my 1979 xl75 frame, rear shocks from an early 1984 cr80, and the forks from a kx60 and kx65 (will go with whichever swaps over better) and a couple donor exhaust pipes to build a stepped exhaust that tucks behind the rear shock and clears the rear tire.

I will also be buying parts to build the motor a little more but will be seeking more advice on that also. Right now Ive got the 75 stripped and I am about to start pulling the motor from the xr.