TRI­TON SPE­CIAL­IST

Dave De­gens, Dresda main man and all-round font of Tri­ton knowl­edge

Classic Bike (UK) - - Contents - WORDS: RICK PARKINGTON PHO­TOG­RA­PHY: GARY MARGERUM

Dave De­gens may not have in­vented the Tri­ton but he made them fa­mous. Af­ter 50 years build­ing Dresda Tri­tons, he has a lot of knowl­edge to share

Dbike,ave De­gens vividly re­mem­bers the first Tri­ton he ever saw. “It was around 1955. It be­longed to one of our crowd, Johnny Gray. He was an en­gi­neer and had fit­ted an iron Tiger 110 en­gine into a very early Manx chas­sis. When I fi­nally blew up my first

a tuned-up G3L Match­less, Johnny Gray towed me home be­hind the Tri­ton and it left a last­ing im­pres­sion.” Mov­ing up to a BSA Gold Star, Dave turned his café rac­ing abil­ity to the track, where the Tri­ton came back into his life. Rac­ing suc­cess with the Tri­umph-en­gined Nor­ton hy­brids prompted the ac­qui­si­tion of Dresda Au­tos, where he built and tuned road and rac­ing bikes. Although Dresda later moved on to tun­ing big Hon­das for the Ja­pauto race team, when Dave re­turned to classic rac­ing in the 1980s, the Tri­ton side of the busi­ness started all over again. Of­fi­cially Dave re­tired 14 years ago, but Dresda is still go­ing be­cause, as he says: “Our cus­tomers rely on us.” In con­ver­sa­tion it’s clear that the racer’s de­ter­mi­na­tion to win is still there, even if these days it’s from the tun­ing bench more than the sad­dle.

Dresda’s prin­ci­pal spe­cial­i­ties are the tun­ing and re­build­ing of a va­ri­ety of en­gines, and chas­sis builds and re­pair, mainly un­der­taken by Dave’s as­sis­tant Rus­sell.

“We still build our own Dresda light­weight chas­sis,” says Dave. “There’s a Honda one in the jig, but we also do a lot of re­pairs and mod­i­fi­ca­tions to Featherbeds. Most prob­a­bly weren’t right from new; the right-hand tank tube is usu­ally higher than the left; they are prone to crack­ing across the down­tubes so be­fore we start build­ing a Tri­ton there’s a lot to do. We weld up any sur­plus holes, gen­er­ally fit a rear loop and a side­stand lug and check that all the brack­ets are in the right place for the en­gine to be fit­ted.

“De­sign­ing en­gine plates isn’t just a mat­ter of su­per­im­pos­ing a Tri­umph en­gine plate over a Nor­ton one to get an out­line. Most com­mer­cial en­gine plate sets don’t at­tempt to find the best po­si­tion for the en­gine. We’ve seen plates that, at full sus­pen­sion travel, leave about four inches slack in the rear chain. We’ve fit­ted all sorts of en­gines to Featherbeds: Vin­cent, Rudge you name it; to do the job prop­erly of­ten the frame needs to be al­tered slightly. To fit a Tri­umph Tri­dent, we spread the lower rails to lower the en­gine; that gives space to re­move the rocker boxes, but also be­cause the Tri­dent rear sprocket is much larger than a Nor­ton, it stops the rear chain wear­ing a groove in the frame strut be­neath the oil tank. When it comes to en­gine tun­ing, Dave says it’s im­por­tant to know what you want. “Some of our mod­i­fi­ca­tions I only of­fer to rac­ing cus­tomers. Most peo­ple don’t want a race en­gine in a road Tri­ton – fit­ting Thun­der­bird cams and softer pis­tons makes a much more pleas­ant bike to ride, with enough per­for­mance for most peo­ple. Many of our mod­i­fi­ca­tions are worth hav­ing for re­li­a­bil­ity as much as speed. Take the light­ened valve gear. We lighten, bal­ance and pol­ish the rock­ers and fit much lighter valves with 6mm stems (5/16in is stan­dard) in spe­cial Col­si­bro valve guides. The weight re­duc­tion means we can drop the spring rate by around 100lb; this en­ables higher revs on a rac­ing en­gine, but also takes a lot of wear and tear off the cams.”

“With the pre-unit en­gines, we start by re­in­forc­ing with weld around the drive side (left) main bear­ing. Flex in the bot­tom end is a prob­lem in tuned en­gines and the more rigid the crank­case, the bet­ter. Ev­ery­body thinks the one-piece Tri­umph crank is the best, but it’s too rigid for the pre-unit crank­case. I’ve never had a boltup crank break but, as per­for­mance in­creased, the one-piece

‘MANY OF OUR MODS ARE WORTH HAV­ING FOR RE­LI­A­BIL­ITY AS MUCH AS SPEED’

ones started go­ing across the tim­ing side big-end. Re­plac­ing the ball main bear­ing that side with a roller, like the drive side, helped – and Tri­umph later did the same thing. For rac­ing we re­in­forced the tim­ing chest, adding ver­ti­cal beads of weld as but­tresses to pre­vent crack­ing across the camshaft and breather holes where the power was try­ing to rip the bar­rel off!

“I’ve al­ways stuck with Tri­umph plunger pumps, I’m not a big fan of ro­tary ones. In the early days I used to sleeve the plungers over­size and bore the pump bod­ies to suit. Nowa­days we use T140 plungers to achieve the same ef­fect. I al­ways took the view that since stan­dard Triumphs rev to 60007000rpm and the stan­dard valve re­leases at around 60psi, you need about 10 psi per 1000rpm. Once I got the ig­ni­tion sorted, my Tri­umph was revving to 10,000 and I wanted more pres­sure; I’ve found you can get 150psi out of a Tri­umph plunger pump.

“Also on the lu­bri­ca­tion side, we use a pres­sure feed to the rock­ers in­stead of pick­ing it up off the scav­enge. It comes off the blank­ing bolt on the front of the tim­ing cover and we find that the in­creased oil com­ing down the pushrod tubes re­duces cam wear by about 30%. We also up­rate the rocker spin­dle seals with two O-rings in­stead of one and a cap over the end. We use thick, pre­unit-type bot­tom pushrod seals and it’s im­por­tant to check tube length and the depth and also an­gle of the ma­chin­ing in the cylin­der head. These of­ten need to be cor­rected to com­press the seals cor­rectly. We do spe­cial O-ring-type tap­pet cov­ers, too.

“When we started rac­ing the unit Triumphs we al­ways had a mys­te­ri­ous mis­fire at about 6800prm. The fac­tory thought it was ig­ni­tion, but look­ing down once I saw petrol com­ing out of the tick­ler as a vi­bra­tion patch hit the carb. Since then, I’ve used rub­bers to iso­late the carb from the en­gine. We make our own from ra­di­a­tor hose ma­te­rial which seems to work best. We also make the adapters for the dif­fer­ent heads. “We run greater pis­ton-to-bore clear­ance these days, be­cause the fuel burns hot­ter. A two or three thou run­ning clear­ance needs to be more like five or six now and we’d rec­om­mend eight thou for an 11:1 pis­ton. The squish on a Tri­umph pis­ton wants to be about 31 thou; you know you’ve got it right if there’s just a black stain around the edge of the pis­ton with no car­bon build-up.

“Belt drive has made a big dif­fer­ence. Run­ning the clutch with­out oil means you can back off the springs to give much lighter ac­tion. We do a spe­cial sealed main­shaft nut to pre­vent oil run­ning up through the shaft into the clutch. We keep a se­lec­tion of frac­tion­ally dif­fer­ent size front pul­leys so that when we set up a unit en­gine we can get the ten­sion per­fect.

“Nor­ton gear­boxes were in fash­ion for a while, but I was never con­vinced. There was al­ways trou­ble with them; I re­mem­ber turn­ing up for a 24-hour race; Gus Kuhn was there with three Nor­tons and said: ‘I wouldn’t bother get­ting out of the van, Dave!’ But in the race all three dropped out with gear­box trou­ble. When you look at it, Tri­umph gears are much meatier; be­sides Tri­umph used to make close-ra­tio sets so I stuck with them. We fit sealed bear­ings to back up the oil seals and we’re of­ten asked to fit five-speed in­ter­nals into pre-unit shells; it only takes a few sim­ple mod­i­fi­ca­tions to clear the cam­plate etc, but there are vari­a­tions in five-speed sets – that star-shaped dog/washer comes in vary­ing thick­nesses, so I al­ways set the gears up in a dummy gear­box with win­dows to check en­gage­ment. We usu­ally re­place the bronze layshaft bushes with nee­dle rollers, too. “When we were rac­ing the big-bore en­gines with Nor­ton cranks, we were up to about 800cc and did have a few gear­box shells crack. We re­in­forced them with weld be­tween the shafts, but they’re usu­ally strong enough. Those en­gines had so much torque you could win a race with­out revving over about 5000!”

So many Featherbed spe­cials have been built that it’s easy to as­sume there’s noth­ing to it. A talk with Dave De­gens soon makes you re­alise that it’s not quite so sim­ple, so maybe it’s as well that Dresda is still around.

‘WE RUN GREATER PIS­TON-TOBORE CLEAR­ANCE THESE DAYS, AS THE FUEL BURNS HOT­TER’

108

Dave’s ‘re­tired’, but Dresda keeps go­ing...

Wes­lake en­gine nes­tles neatly in one of Dresda’s own Light­weight frames In Dave’s rac­ing days beads of weld were used to re­in­force the crank­case weak points Dresda’s light­weight valves and softer springs in­crease rpm and re­li­a­bil­ity

Rub­ber mount­ing keeps the fuel from froth­ing Spe­cial tap­pet cov­ers are machined to ac­cept O-rings

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