onthegas

Not the best photos. The first two are of a plug with ~2 hours on it. The second two are of a plug that has been in the engine for roughy three years. Both plugs are NGK BP5ES. The bike started mis-firing when riding WFO. It would still idle, but would mis-fire under load (mainly my fat a***). Carbs are clean on all three bikes.

Points, condenser and coil were replaced ~10 years ago. Bike is only ridden 2 to 3 times a year. My sons Honda has an ignition that’s 2 years old and his TY80 had the points and condenser replaced 3 years ago, probably the original coil. The trouble on all 3 bikes started after using leaded race gas and after running at full throttle. The spark plug has some deposits (I’ll post a photo later). Each time changing the plug solved the problem short-term.

Over the weekend I competed in a vintage trials and a poker run on my M98 “Sherpina”. Both had some high-speed open field sections where I had the bike WFO in 5th gear. Twice the bike began to miss and sputter at full throttle. Changing the spark plug fixed the issue. Looking for an answer I discovered lead-fouling of spark plugs. This is more common in aviation, but it seems to make sense. Back in May I purchased some leaded race fuel, Trick 110, which I mixed 50/50 with non-ethanol premium (92 RON+MON/2), for running in my vintage motocross bike which needs the higher octane. Since I didn’t want the fuel to go to waste, I have been using it in other bikes. Two of the bikes my son rides/races have developed intermittent spark issues. He’s only 13 and hasn’t been able to fully explain what’s happening other than the motor dies. After my experience this past I believe the issue lies with the fuel. Has anyone else had a similar experience?

Were you the guy riding the M85 at the Rattlers Run AHRMA trials over the weekend?

Make sure to disconnect the black and green wires from the terminal block then connect the multimeter to the wires coming out of the stator. You can test this by manually opening the points through the slot in the flywheel. Resistance should then go from zero to infinite on the meter.

I have an M98 "Sherpina" for vintage trials and an M206 Pursang for vintage motocross. My running joke is when Bultacos were new brakes were optional, but they came with a couple extra neutrals. First thing to do is make sure the hard chrome is still present in your brake drums. If it's peeling or gone they can be repaired. Some shops will install a steel liner and others will flame-spray metal into the hub then turn it on a lathe. Neither repair is cheap and both have their positives and negatives. I'd also recommend using grooved brake shoes and having the shoes fitted to the drums. You can find instructions on how to do this all over the Internet or pay (big $) to have a shop do it for you. It is labor intensive. As far as more power goes there's not a whole lot that can be done short of putting a 325/350 motor in the chassis.

Thanks! Actually it's an M98, 175 Alpina. The M97 was a 125. The 175 & 250 (M85) have the same stroke and most M98's, including mine, were fitted with a 250 jug and piston by the dealer. I did split the cases, but reassembled with new gaskets and Yamabond sealant. It's also not burning gear or trans oil, but the ignition side seal could be leaking though I didn't see any signs of a leak when I pulled the ignition cover to check the timing. I know it's not a plugged pilot jet, brand new carb, and I checked for air leaks on the mounting surfaces. I'll try adjusting the air screw first to see if that makes a difference. Also I installed a new fuel tap last year and it's flowing plenty of fuel. Gearing could also be an issue. Before installing the M91 gears I had a 50-tooth sprocket on the back. I went back down to the stock 42-tooth sprocket after swapping out the trans gears. Guess I should try the simple stuff first.

I have an M98 Alpina that I restored to running condition 12 years ago. A couple years after that I turned it into a "Sherpina" for riding vintage trials and rode about a half dozen trials. Seven years ago I was given a basket-case M91 (that had been in a fire). The gears, heavier primary-side flywheel, single-row chain and clutch basket from the M91 made their way into the M98. Shortly after that I moved and only used the bike to ride around in the woods following my kids when they were learning to ride. Last year I entered my first trial, in six years, and noticed the bike was having some issues, but figured I was just rusty at riding trials. This year I picked up a TL125 and a TY80 for my boys and I to ride trials together. Last month we entered a trials and I was having a lot of carburetion issues, so I pulled apart the Amal and found the slide was worn out. I replaced the old Amal with a Mikuni VM26, checked the timing (still in spec.) and cleaned the air filter. All the old problems (hard-starting, flooding, running lean) have disappeared. A couple weeks ago I went to a friends place to practice for a day. One thing I noticed was when crawling through a section at idle the bike lurches to the point where I have to use the clutch and throttle to keep the engine speed up. It was doing this with the Amal carb too, but the other problems sort of overshadowed this one. This makes the bike very difficult to ride in tight sections. I can ride the TL or the TY in the same tight section and not even touch the clutch. Lurching was never an issue when I rode the bike before in competition. After I swapped out the internal parts with those from the M91 I never rode the bike in competition. I'm thinking the heavier primary-side flywheel is the culprit here even though the. engineer in me says a heavier flywheel would have the opposite effect. Has anyone else experienced a similar issue?

Half the fun of owning an old Spanish bike is working on it. In fact I get just as much joy working on it as I do riding it. If only my modern bikes were as simple as my Bultaco. Of course, back in the day, simplicity was needed since you had to work on them all the time. Then along came those darn Japanese showing us what the term reliability really meant.

As has been stated previously in this post, the black wire coming off the LT coil and connected to the ignition points, goes to the HT coil. The green wire goes to ground or, as you say across the pond, earth. Make sure you have the green wire grounded to bare metal on the frame. The red wire, which is soldered to the yellow wire on the LT coil, is for the brake light. Relocating the condensor to underneath the gas tank is an old Bultaco trick. The condensor gets extremely hot down in the ignition and breaks down over time. At first the bike becomes hard to start when warm. Then it will quit and lose spark after the bike warms up. Eventually it loses spark altogether. Moving the condensor gets it away from the heat source and puts it in a place where it is easier to replace. The ignition system doesn't care where the condensor is, it just needs to work to prevent arcing across the points.

The following PPG paint codes are from the bultaco.com (Hugh's Bultaco) website: Bultaco Red = Torch Red DAR 74013 Bultaco Silver = Crystal Silver Metallic DAR 34926 If adjusting the clutch doesn't help, the plates might need to be deburred. I did all that to mine, but still had a bit of clutch drag. Also stock Bultaco clutches do not like to be feathered gently, instead they grab. Although there is quite a bit of controversy, what I did was replace the 30wt engine oil in the clutch with Type F ATF. This has eliminated the drag and the grabbing issues.

Are you kidding? The environMENTALists would never allow us to desecrate sacred tribal land with an off-road vehicle!

swooshdave is correct, I'm in NY. Thanks for the clips. Hard to imagine 90 starters at a vintage, excuse me, classic event. I've ridden enduros with fewer entries. MAVT is the nearest vintage series to me, but the events are quite a haul just for one day of riding.

I just started competing in observed trials this year. Although the word "compete" is a bit of a stretch for my feeble skills. My bike is a Bultaco Model 98 Alpina with a Sherpa T slimline tank/seat, aka the Sherpina. I've ridden a total of three trials so far. The first two events were modern trials. At the first one, the sections were way over my head and I had a solid lock on last place when my kick-start lever fell apart resulting in a DNF. At the second, the sections were much easier and I did a little better despite having issues with a clogged fuel tap. Even beat a couple of modern bikes. Those guy must really suck! In August my club, CATRA, held a Vintage Trial. Sadly there were only 6 vintage bikes competing. Two in twin-shock expert, three in twin-shock intermediate and myself in twin-shock novice. Rather than take an easy trophy I rode in the Intermediate class, got lucky and snagged some hardware for second place. Section 1 Section 8 Coming from an enduro/hare scramble back ground, trials is a lot different. However I didn't have a whole lot of fun until the vintage event. There I was able to ride with others who have a lot more experience and was able to pick up some pointers. I'm not ready to give up riding enduros, but I'm looking at buying a used modern trials bike.

Is this the Upland Enduro? Pretty sure I rode it once a few years ago when I lived in the midwest. If I remember correctly (it's hell getting old), they used AMA Qualifier Rules with a Known Control check-in format. Pretty much what the AMA Nationals are using now. I left the remnants of a KDX fender along the course as well.

Course splits are generally used to give A & B riders an additional timed test section. Occasionally a C rider won't be paying attention and go the wrong way. If the extra section is at the end, it's usually not a problem. If it's in the middle, it can result in a heated debate during the protest period. Personally I like the idea of making everyone ride the same route. That way a C rider can see how competitive they are against B riders. It also makes it easier to pick out the sandbaggers. The Barbed Wire Enduro (in PA) that has an incredibly steep and slippery hill with an optional go-around that is longer, but the club puts it in a transfer (non-timed) section. Eight miles is a pretty decent sized test section. With a 24 mph speed average, a rider would have to make it through in 20-minutes, assuming it's a check-in, check-out format, to score a zero. You might consider alternating the trail between the grass track and the singletrack and finish the section with a half-mile grass track sprint, if possible. I know when I've ridden sections set up like that I'd come out of the woods thinking "great, this section is almost over" only to be dumped back into another 2 or 3 miles of singletrack.

I'll probably take some flack for this, but what's fun for a trials rider can be downright brutal in an enduro. Particularly if it's combined with a high speed average. In an enduro riders are racing against the clock over natural terrain. Using obstacle after obstacle to try and take points away from the riders (by making them late) can be a recipe for disaster. Some C riders will hour out just trying to get through/over/around a difficult obstacle. If you have an obstacle that causes riders to back up it won't take long for singletrack to look like a superhighway as riders start making alternate lines. The times I've been "trailboss" for an enduro I've always tried to keep it fun. Some clubs tailor their enduros to the A and AA riders, but you have more B and C riders at an enduro and these guys are the future of the sport. Also remember that the weather can have a huge impact on the trail conditions. My favorite enduros used a lot of tight singletrack where you had to weave back and forth between handlebar width trees. Combined with the correct speed average you can take points from expert/pro riders and not hour out all the novices. Log crossings are not unusual, but keep it simple. A foot or less in diameter and don't have log after log. The only one who'll be happy after an enduro like that is the parts guy.

I've ridden a couple trials on my '73 Bultaco "Sherpina" (Alpina 250 w/a Sherpa T tank). I ride enduros on an '03 Gas Gas EC300. The Bultaco is much easier for tight, slow-speed maneuvers due to the short wheel-base and lower center of gravity. The Gasser has a better motor for powering through stuff and, of course, much better brakes.