This handsome 1969 Triumph Trident first came to us back in 2016 for extensive work. We machined the cylinder head to accept o-rings so that we could repair an oil leak, repaired the rod bearing which had clearance beyond it’s specifications (therefore causing “knocking”), and got it running well.
While it was here, we appeared on the TV show Out N’ About Columbus and Mike Kilburn (right) happened to sat upon the Trident during filming for the bit’s opening scene. To view the video, click here.
It’s now back in the shop a few years later because it’s fouling the spark plug on the right cylinder.
After checking the compression we ruled that out as a possible culprit of the undesired symptom and instead cast a suspicious nod toward the carburetors. It appeared new carburetors had been installed at some point since last being in our shop, and we could tell they were not able to be synchronized due to the specific carburetors installed lacking vacuum ports entirely.
Synchronizing the carburetors simply means to tune it so that all cylinders are running at the same speed or drawing the same amount of vacuum (the drop in atmospheric pressure). It is vital to have synchronized carbs, as when they are out of sync they can create a host of issues- anywhere from rough idling to fouling plugs.
To repair this issue, we had to come up with a way to synchronize the carburetors. First, we drilled ports into the side of the carburetors. Then we tapped them, allowing both our vacuum gauges (similar to synchronizing sticks) and later plugs (so that upon completion we would not have an air leak) to thread into the ports. With viable ports, we hooked up the vacuum gauges and ran the motorcycle.
The vacuum gauges measure the amount of vacuum that each cylinder is pulling. As we suspected, the carburetors were severely out of sync. The left cylinder was carrying the motor by a landslide, therefore explaining our running/fouling problems.
As indicated with the green arrow below, you can see the allen head bolt that now serves as a plug for the vacuum port that we drilled and tapped.
We repeated this same process on all three carburetors (hence the name “Trident” – it has three cylinders as well as three carburetors). Once complete, we test rode the motorcycle and were pleased to find that the symptoms appeared to be alleviated.
We’re now in a holding pattern awaiting an opportunity to test ride it even further but have no doubt that this beauty will be back on the road again soon!
