Well after the first of the month I’m off to Orange County to pick up that 250 SL Model 70A after all! Andrew couldn’t bring it during the move to Ohio. After a few weeks, he went back to California and said good bye to Ohio! So I spoke with him on Facebook today and told him I would drive out and pick it up!
Now, it’s the enduro model with all the lights & the bike is 100% complete, according to Andrew. It even has all the original plastics. It is siezed, but only has 1300 miles on the clock! He thinks it’s the bottom end that’s frozen up. So maybe just crank bearings? But I’ll do the whole thing to make sure it’s fresh!
Now, what are the special things I should be looking at with this particular 250SL Model 70A! What are known issues and the known work arounds for them? I remember the issue with the head not being the best it could be with some of the 250’s but don’t remember if it was for the SL or the ED with out the lights? I would appreciate any and all feedback on this Model!
OK! Well that’s one to certainly consider. Is there anything else? And any specific tricks to cutting the ED head neatly & safely?
And Rich, would Any type of head work like grooving lines in it make the SL head more viable? I sure don’t want to be burning up Pistons. Thicker copper head gasket maybe? Victor
If you're gonna have it apart to check things out, now's the time to refresh all the bearings and seals and gaskets, doesn't make sense not to. And add any up grades that may be recommended .
Here is the heads in comparison. I cut mine with a cut off wheel and my die grinder. And there are many mods that can be done , its best to call me if you want rather than spend a lot of time typing . Mine has many, Port work , reeds , UfO in carb, gutted pipe , shaved flywheel , runs pretty good
You are on the right track with the head. I spent years chasing spark knock with the stock head.
The other BIG weak point with all 250s is the kick start lever. The splined portion was way to short to handle the force needed to start the engine. Most levers are stripped or the shaft is stripped and they have the kicker welded on. Paul used to sell an upgrade kit which required splitting the cases to install. If you have the engine apart to do bearings, you may want to consider this mod.
To bad you couldn't have checked it for spark. The mag covers leaked damaging the stator and the unit itself was weak. Replacements are scarce.
With all these defects, I still loved riding the SL or ED. They were smooth and very comfortable.
another reason for spark knock is the cdi box that advances on upper rpm that's a no no. Here is a pic of the reeds I fabbed for myself as well as a customer . At first glance it looks restrictive but the air actuall has a pretty straight path through the manifold. And I got the carb to sit in the stock location.
Spark knock is a non-technical catch all for either detonation or pre-ignition. I suppose one would need to determine which is actually going on to know how to fix the problem. Detonation can be as simple as backing off the timing to go with the gas you can get, or buying better fuel with a higher octane rating to go with the ignition you have. There are other ways to address detonation if it is a function of compression ratios or chamber design, i.e., squish band, off center spark and chamber, or whatever.
Pre-ignition would be more likely a result of extreme hot spots and debris in the chamber causing combustion from an alternate ignition source than the spark plug. I sorta doubt that's what's wrong with the 250 SL setup.
Advancing timing at higher rpm would only be appropriate if the engine design called for it, and I can't see where any Hodaka is actually designed to need advancing timing at the extreme upper range of rpm. I have to wonder what the Japanese engineers had in mind in using such a system, or if perhaps they simply didn't check the advance curve on the CDI that they outsourced when they put the 250 together.
If you can't find or can't afford to swap out the CDI that comes stock, back off on initial timing so that total advance at high rpm isn't past a usable point, but this will probably also take away some snap at the bottom end. It might start easier, but it might not pull well either. Otherwise, if there is a compatible and correct CDI from some other bike that someone can readily find on eBay, find it and swap out the system. Are we talking about a 250 Suzuki of some type or other?
Last question is whether changing heads as discussed obviates the need to swap out the CDI, or if the ignition also needs to be changed regardless of head swaps.
the Suzuki box advances also. When I built my trick 250 I used the tm 250 stator and rotor and started with the Suzuki box that how I found out . So I ended up using the supercombat box which retards on top but lacked advance on the bottom but by slotting the suzukt stator plate to advance base timing 5 degrees I got it to work great. But My SL still has the stock box and even retarding timing 5 degrees it would still ping under high speed load and by swapping the head for the ED head it all went away. I recently took it out and ran it hard with no ping , it pulled 75mph on a slight up hill climb and was still pulling with no sigh of the little man with the hammer inside
So. I’m I looking at a lot of work to make the 250 function well and avoid the head piston problems I’ve seen & read in other posts? Is there no way to address these issues without all the changes Rich has described? I’m not looking to make a 250 racer out of it. Just wantvit to be something dependable, which I can run at the local practice track or out trail riding with the grandsons and not have to worry about it leaving me stranded somewhere.
I’m going to have to drive 1600+ miles round trip to pick up this bike. If I’m better off getting a comparable Yamaha or Suzuki 250 2 stroke, abs avoid all the complicated issues with this bike, I’d rather know now. It will cost me between $250 & $300 in gas just to go get it & bringvit home. If I can spend $600 on a used Yammie or Suzi and getvit here, or a lot closer, I would consider that. So, honest opinions, PLEASE!!! Victor
So Rich. Here’s a question for you. Is there a significant difference in the performance of the SL head because the plug is offset, or is there also a bigger change in shape of the SL squish area compared with the ED head squish area? Or is it just the photo angle causing distortion? The SL head in your photo looks to have more volume than the ED head next to it. Victor
I realize that the 250 SL is not as simple motor as the Ace, Toads and Model 94 Wombats, but besides the head differences & The CDI ignition, what else is different about the motor? It’s not reed valved, right? Does it have a much more complicated Tranny than the Aces, Toads & Wombats? And I realize it shares VERY FEW parts in common with the other, smaller displacement bikes. So please share with me some of the other significant differences in both the top ends & trannies! Victor
Top end and tranny are principally the same as the 90-125s, just bigger. Clutch is conventional though, i.e, not mounted to the crankshaft. Actuation mechanism for the clutch is also the same but the parts aren't interchangeable.
Dimensionally the 250SL is a larger overall bike than the Yamaha, Suzuki, et al. If you're a bigger and taller sort of guy you might appreciate the extra room to stretch out. There is a stock '76 Honda XL350 and a '75 DT250 in my neighborhood but the less-refined 250SL has more appeal and style for that reason than its more put-together and mass-produced peers.
I've ridden mine about 5,000 miles so far, but have had to split the cases three times at this point. First for the initial rebuild (including kickshaft upgrade) and the latter two for a holed and seized piston, and then a sheered countershaft.
A detached carburetor float appears to have caused the condition that melted the piston, and I suspect the countershaft wasn't properly tempered from the factory. The original countershaft had been heated but maybe not quenched to finish the process -- I suspect so because the shaft was soft --it scratched easily with a file. This might have been a Detroit-style Monday or Friday production deficiency.
The 250's have more in common with the model 03 than the earlier Wombats or Ace series. Transmission is similar in that it is a constant mesh, but it is primary kick start so has those few extra parts inside. It is also oil injection, and so has the pump parts as does the model 03.
The combustion chamber is offset on the SL which creates a very asymmetrical squish band. I think doing away with the asymmetry is the point of swapping in the ED head.
I would definitely follow the CDI redo just to avoid issues.
My question would be why the bike in question is "locked up." If the engine is seized and the cause is not known up front, it is a parts bike potentially. All depends on what went wrong inside. If the transmission is trashed, new gears will cost more than the bike is worth. If the piston is just stuck from sitting too long, it might fix up easily enough.
The odd ball Hodaka I like is the 175. That was a cool bike that didn't get enough recognition.
Got some pictures from Andrew on the 250. It’s now a dead issue. The minute I saw this head & cylinder, I circled the areas in red and told him why. Zoom in on the red circle areas! Victor
Time to source a new top end, maybe a ED cylinder and head? The reed set up in a previous post almost looks like a "down draft" unit, kinda cool. And as for upgrades, you can pick and choose which ones you may want to use, don't have to do them all.....
Victor, you might consider getting that jug to Charlie Brown of Superior Sleeve in Portland, Oregon. If it is salvageable, he'd be the one to do it. He did a sleeve job on an RM250C2 cylinder for me and it has been flawless for over 20 motos.
Well, you knew it didn't run, and apparently he had the same problems everyone else has.
This looks like your typical piston failure following some heavy detonation. No doubt the ring fragments also made their way into the bottom end and took out the bearings.
But I can't make out what it is you circled in the photo of the cylinder. Did he chisel the head loose with a screwdriver? Not clear to me from the photo.
It’s kind of fuzzy but there’s a chunk missing and also looks like a possible crack. It’s a moot issue. I passed on the bike. Way too much work needed for a $5-600 investment. That cylinder doesn’t even look worth trying to save to me. I see way more than $1000 going into that bike to make it functional.
I decided instead to rebuild the Model 03 motor I got & put it into the Model 03 chassis. Then get a Model 94 or 94A chassis and move the current motor into that! Victor
Victor
Victor