Vintage Bike Tech Tips

Elsinore 125

TIPS AND TRICKS FOR YOUR HONDA 125 ELSINORE

By Rick Sieman

Quite possibly the best 125 vintage bike ever built, the Honda CR 125 Elsinore.

We’ve told you on more than one occasion that the 125 class is the most expensive class you can ride and we can easily back up that statement. Because they’re revving ultra-high all the time, and you’re constantly shifting like a maniac, things wear out and simply fail at an alarming rate.

Quite possibly the most popular and effective 125 class vintage bike, is the 125 Elsinore. This ultra-light and powerful bike was a total breakthrough in its day (it debuted in 1973) and had a nice model run of several years before it changed.

This article will not be a hop-up article per se, but rather a hefty piece of advice on how to keep your Honda CR 125 in one piece.

The Honda manual tells you some of the things you must do, like changing the rings every three races, but they don’t get right down to the serious stuff that’s necessary for keeping the bike alive and well.

So here’s realistically what you must do to keep your rocket alive and well for the vintage class racing. Additionally, included are tips about chassis weaknesses and basic bullet­proofing of the whole package.

MORE STUFF YOU GOTTA KNOW!
General information: It’s going to cost you a lot to keep a breathed-on 125 Honda in the winner’s circle on a regular basis. Try to cut corners, and it’ll cost you even more.

• The TM-250 Suzuki intake manifold works just fine with the 34 Mikuni carb.
• When installing new main seals, you must slip the crank into the seal at least five times, regreasing it each time. Otherwise, the odds are you’ll pinch the seal when installing the crank. If you don’t do this, the motor will only run five minutes hard before it blows.
• After you replace the third and fifth gear in the transmission a few times, it’s best to replace the whole gearbox.
• If you think the information presented here is B.S., then try to campaign one of these baby rockets on a minimal maintenance budget and see what blows first.

Honda 125 fork seals do leak when the bike is ridden hard. To keep them from leaking, insert a narrow screwdriver into the top lip of the wiper and fill with WD-40. After pumping the forks a few times, wipe off the residue and go riding. This will at least double the seal life, and it will make the fork action smoother.   Front wheels should be laced up with 8 gauge spokes. The stockers might be O.K. under a novice, but won’t hold up under a hard rider. Here’s what can happen to the stock wheel.   The front brake has to be de-glazed after each and every race. 400 wet-or­-dry paper works best for this. After sanding, clean the drum and the shoes thoroughly with contact cleaner.           Naturally, the stock dampers and travel don’t cut it. Try to locate a old Poppy kit 7½ inches of travel, or the Fox Kit 7½ inches. The Fox set-up also used air caps. There’s a lot of flex in the forks, even with new dampers. Nothing much can be done about it; the stanchions are just too small. Factory bikes and the new production bikes were 35mm; older units were 33mm.   The steering stem stretches easily and makes it difficult to keep the forks tight. Every third race, the bearings should be repacked. Steering head does not need reinforcement.   Kick stand has to be removed, or the frame will break in the indicated area.           Gusset below steering head tends to crack where the accessory mud flap bolts in place. It should be brazed shut.   Where the cradle and the downtube meet, there should be a gusset welded in. This is a critical area. If the front cone-on the exhaust pipe keeps cracking, this is a dead give-away that this area is cracked, even if you can’t see it.   A hole must be drilled in the shift lever, It’s quite strong and won’t break if the bike falls on the left side. If it doesn’t break, the shock is transmitted to the gear box, which can be expensively wasted.           The ‘74-’75 bikes do not have to be reinforced in the peg area. Older models must be beefed up.   Rear motor mount tabs must be reinforced, or they’ll eventually break and fall off. They should be welded on both sides.   Rear tank mount will crack. This is usually caused by the frame mount cracking.           Here you see a frame mount in the process of breaking. This entire area should be reinforced and still looked after regularly.   The area where the rear loop joins to the backbone is also very weak and should be strengthened thoroughly.   1973 and 1974 bikes have 8 millimeter sprocket bolts. The hub must be drilled out and ¾" x 2 ½" bolts must be used. The area inside the hub where the ribbing comes down must be slightly relieved for nut clearance.           Standard 428 chain doesn’t cut it. This is one of your most important modifications, as chain tossing and resultant damage is common with the stock stuff.   With any sort of forward mounted shocks, you have to use a chain tensioner.   If you modify the stock swingarm for increased travel, this is how far you must run the gussets forward. Any further, and the chain will saw away at the metal, possibly creating a derailing problem. This is also where the swingarms tend to break.           Stock rear spokes are strong enough for the most part. However, they should be changed to eight gauge units if the bike is going to be run in the desert. For motocross, the stockers hold up. Reason for this is the fact that they have a large shoulder that tapers into the final spoke size. Rims need not be fooled with, or changed.   Rod clearance must be widened to .020-.022 in order to let the bottom end live if the engine is modified. Stock is .016. When replacing main bearings, use a 305W Delco bearing. The oil groove should go toward the inner part of the crank. The big difference between these and the stockers is ten balls for the Delco and seven balls for the stockers. More balls always let you go faster; that’s a fact.   Engine details: Run a quality mineral oil at 32:1. The Honda piston is used stock, with no additional oil holes drilled. Top end bearings should be replaced after each two races. The Delco bearings should last about six races. Rings—every race, should see a replacement. Stock rings go for $8.70, but in some cases stock and second over, Suzuki TM-125 rings can be used in the top land when a single ring is run. The TM rings cost only $5.00 and seem to hold up longer. Remember, this maintenance required for Expert-level racing!           Stock pistons tend to crack above the pin boss on the sides of the skirts. Keep an eye on this critical area.   Don’t use heavy-duty clutch springs. They tend to pull the threads out of the guide. Replace the stock ones often, perhaps every four to six races.   SL-100 clutch plates work well. They’re .020 thicker and cost less than the Elsinore parts . As soon as the clutch starts slipping, replace the plates. Maybe every ten races or so.