downunder

SSSHHHHHHHH I'd better be quiet........Howard knows who and where I am!

Howard Neat photo editing trick you have done there! Of course all us here downunder know it isn't really fibreglass, it's just a Revell model that Howard built and pretends it's real!!!!!!! Sorry Howard.......just couldn't help it I have this one in the shed ready for a cut down to make my next pick up! This it what I want it to end up looking like when it is done! I thought I might be able to fit two bikes on the bonnet 'cause it's longer than the back!!! BJ (now I've done it) Downunder

Charlie Go back to page#2 and read what Howard said about the oil system of the Sherco 4T. To me it makes sense to build an trials engine as simple as possible. If that means things like oil pumps and fancy electronics can be left for Moto GP and trials focus on lightness and strength that's fine. I'm sure riders who do their own repairs at the SSDT would rather have a set of Allen Keys than a laptop computer. As far as 4 strokes running a higher engine temp goes, I'm still not really convinced they do, lets face it if it isn't boiling it isn't overheating. XL250 Honda's of the 70's and 80's could run for ever only using minimal cooling fins on bulky and heavy engines. The 2 strokes of the same era used big fins to keep them cool (see photo 1983 360 H7 Montesa). Which engine did run hotter???? Or does the 4 stroke have a greater capacity to operate better at high temprature? If that is the case then the 4 stroke motor could be the best on a hot day???? BJDownunder ps. At least I know how the 4T gets oil to the top end now, thanks Howard.

SHercoH Maybe aircooled 4T's like the Scorpa 125/175 is the way to go! If they don't boil they can't overhead! I never seen an aircooled motor boil yet But Howard, how does the Sherco 320 get oil to the top end??? I know you know BJDownunder

HondaRS Like I said, crankcase pressure does get the oil up the top end, so did the Husaberg use grooved rings I must find out how the Sherco does it, at least now I know the old Honda didn't just rely on me falling off often enough to get fresh oil up there. Mind you with the amout of time I spent picking it up, it didn't need an oil pump BJDownunder

G4321 I stand corrected although I can't recall a pump on my 78 XL100 but I think there was possibly an oil gallery that ran up beside one of the cylinder bolts so if it had a pump that was were the oil found its way up to the top end. If you really want plenty of oil up the top just crack a piston from gudgeon to gudgeon at high rev's. That tends to force it up and out just be ready for the walk home Come to think of it........do I really want a 4t again????? BJDownunder

Hi Guys n others 4t's run hotter 'cause all the running gear upstairs holds heat and slows disipation, so higher mass (weight and density) takes longer to cool. Just the fact that the camchain puts a gap between the outside world and the cylinder decreases disapation. Provision of space for a camchain alone makes it more difficult to get coolant around the cylinder in a small compact engine. Because of this there is a greater need to provide a cooling system that can cope with the increased retention of heat. But for those of us that rode bikes pre water cooling just think what they had. The 2t's had massive great fins on the cylinder and head while the 4t's like old SL/XL/XR Honda's had next to nothing but ran all day. And believe it or not they had no oil pump, the camchain splashed through the sludge in the bottom end and dragged it up to the top end. Hell, the early Honda's didn't even have bearings for the cam, it just ran in the alloy head. My suspision is that the compession by-pass through rings combined with a breather out of the cam cover carried enough oil vapor to do the job. In those days you could hound a motor for many hours but the eventual wear in the head on the early Honda's tended to be the biggest cause of worry not the heat. More than willing to be corrected............. BJDownunder

Blind Holes???? Hey guys, this is an interesting topic as bolts seem to strip and break off anywhere anytime and getting them out is a constant problem on anything mechanical. What I am not sure of though is the blind thread???? Is the breaking and stripping caused because the bolts are bottoming out??? If this is the case, is it a matter of making sure bolts are say 3mm shorter after allowing for the closing of the pinch clamp? I would have thought that if the bolt never made the bottom of the thread it should not matter whether blind or drilled through. I do like the idea of the dowel used a drill centre guide I will remember that trick!!!!! BJDownunder

Hi All The issue of 4 stroke noise and 2 stroke noise is sound frequency. At a trial here in Australia earlier this year I had professional sound levels taken. Although no 4RT's have found there way here yet the results were quite interesting. Some of the highest noise levels @ 20m were generated by the normal run of the mill Gassers, Shercos and Beta's while at idle. The reason being is the noise at idle is a lower frequency than at revs. Even though the high rpm noise is louder in dBA it looses power faster over even short distances than the deeper pop pop at idle. The 4RT and any 4 stroke will have a noise that is more audible over a longer distance. This is why the 4RT can pass a sound test at similar levels to a 2 stroke but be more audible at a greater distance. BJdownunder

Hi All On the topic of intergchangable rear wheels????? A friend of mine is looking at picking up a 4RT if any ever get to the land of Oz. Will the spare rear he uses on a 03 280 Gas Gas fit the 4rt????? The same wheel fits my Sherco. Downunder Turning Mountains into Mole hills (or was that the otherway around????)

Lets face it............. If you learnt to ride in the good ole days you soon figured out that 2 strokes were peaky and had a powerband that let rip when it pleased itsself. The loping ole 4 strokes used a wasted stroke to act as a flywheel to carry momentum. In recent years (post YZ's) 2 strokes were fitted with heavy and even double flywheel to give more torque and a long exhaust with no chamber to tame the savage beasts. Now we are entering a new era (ummm since 1972???) where exhaust emissions govern what is manufactured. All the same, a 4 stroke was more subtle than a 2 stroke and power to ground has generally been the 4's domain. When it comes to traction we need to remember thrust v mass is the main factor (Danny Pedrosa). A 2 stroke always offererd a weight advantage over a 4 stroke in the past, thus potentially more traction when in the right state of tune but less efficent on fuel and emissions. Now we have 4 stroke motors that match 2's in weight together with engine management systems that smooth out power curves and get the best traction. 2 stroke v 4 stroke is a thing of the soon to be past. Get a grip on the throttle and learn to ride what we all have to live with, love them or not. Downunder

Hi all Just saying hello from downunder and waiting for opinions from people that have touched, smelt or snuggled up to their new 4RT. Looks like we won't see one till April unless we are very lucky. At least after reading the UK posts I know next week = next month and next month is too far away to worry about! ps. can I cut n paste my pic so it looks like I'm standing beside Dougie or has that been done already???? Downunder (where men are men & bikes are are longtime getting here )