atomant

Theres a variety of questions to be asked before you can arrive at what is the 'optimum' engine size for a 4 stroke trial bike but it goes without saying that adding more HP for a given weight will give more power output. So the question here should really be power to weight ratio. At the moment, the bike with the highest performance for this criteria is the Sherco 4t. Mainly depends on what weight you are and what you want to do with the bike! if your'e 8 stone fully wet and you ride the beginners route.. get a beta 80

Well, I've had my 4t for over month now and riden it for quite a bit. Theres been a few problems to sort out but nothing major and I really like the bike. however, There has been lots of talk about the 'complexity' of the 4rt's fuel injection system over the 4t's carb. What happens if it goes wrong? cant fix it coz its too high tech! Have to take it to the dealer and cost a fortune etc etc. My original thoughts were based on the security of undertsanding the 4t's 'traditional' set up but I drive a car with fuel injection and it doesnt bother me so why should it if its on my bike? Fuel injection on cars is extremely reliable and trouble free. I havent heard anyone having any problems with it on the 4rt either so its clear to me that the new breed of 4 strokes should all go this way.... Including the 4T ! If Sherco persist in staying with the carb, then I feel they are missing a big opportunity. Scorpa's new 4t is in the same position. FIM regs mean 4 Strokes are the future, and the future is fuel injection IMHO

Now that is funny - and no, I have nothing against nor dislike the 4T before all you owners jump on me, I just like a bit of dry humour.... Yeh, fair play, I thought it was funny too

so your keeping the 4t then dixie?

A lot has happened in a year! New rulings forcing the manufacturers to make 4 stroke motors and for them to be competitive, they need to be the dogs bollox. My 4t is 3kg heavier than the 2t and i cant notice it at all. The first outing of the 4RT was winning the world series until Dougies accident . You gotta admit thats impressive! This scorpa looks to be around 70kg in weight so hows that heavy ? Its a nice looking bike and if it rides like it looks, there will be a lot of peeps switching to 4 strokes, especially clubman riders like me as they are so much easier to ride. How many peeps have put a stone on in weight in the last year ? !!! IMHO

Oh no no no no no.. Just the clever bits is all i need

That link you gave there RS was an interesting read.. It looks like that PGM-FI system is completely self contained and could be ported to another machine. I'll have to find out what it costs..

RS, Do you know any specialist peeps who know about this stuff who I could ask? Im interested to know how the firing sequence works and does it advance and retard the timing of it depending on RPM ? thanks

Does anyone know much how the Injection system on the 4RT works yet? Would be interesting to mod the 4T and put injection on it to see what effect it has ?

No Howard, To the contrary, it runs very hot but no problems at all. Fan kicks in for about 80% of the time on a hot day. If it was on all the time then I would think it would be boil for sure

5 titanium valves and 249cc .. is this gonna be underpowered. ??? Also, it does look heavy in the engine department so what do you think the weight will come out at ? If it does 70kg or better then it will be impressive. The exhaust system is slick.. really like this idea.. no more burnt legs

Do you have problems starting it when hot when the bike has been turned off normally? say, you just come to a section.. turned it off for a few minutes.. then go to restart it again and have problems then? Coz if you do, mine hasnt got that problem. It nearly always restarts first compression kick. What it doesnt do though is restart easy if i stall it in a section of lay it down on a bank in a section and the engine stops.. can take 5 mins to get it going again Will this help with curing that problem?

yeah, the first trial bike I got to play with was a BSA Bantam 175 and it was always breaking down. Normally the ignition system. But, it seemed the norm to have bikes breaking down all the time. Something we got use to i suppose. Honda make great bikes, I agree with that. The 4t needs some work to get it sorted but I dont seem to mind strangely enough. Its fun taking the thing apart and working out what does what and coming up with ways to improve it. I get a buzz out of it. But im certain that when its sorted, its going to be a great bike If you 4rt owners are going to Hawkstone, I'll buy you all a pint and we can chat about 4 strokes till dougie wins

Yeah, its typical of peeps who are passionate about something! At least we all have something in common, we like 4 strokes

Nah, not boring having one that starts first time.. Just boring riding one

RE500 Can you please expand a little further what you have done ? Do you have any photos or anything? Thanks

I've done 4 trials and on my 3rd oil change from running in. It sounds real smooth now I will change the oil now every 4 trials purely for the reason you state.

Sherco's idea of extending the oil capacity to help with the cooling only has a limited effect on reducing the heat of the engine, unless like you say, the oil is being pumped and externally cooled. All it does is add more thermal mass but without an obvious place for the heat absorbed to be dispersed, its going to get hot and retain its heat for longer. This is what I experience with it.. Its gets VERY hot. But, whats interesting is that it seems to cope with no problems at all. Their testing ground being in spain must be dam hot so they must of been happy with it to release it for sale.

Unless you know something I dont, I dont think they will go with an oil pump.. more cost and more weight with an oil rad needed also. The solution would be to make the current system more efficient. I think Josep Paxau is obsessed with keeping the weight down so Im not sure what he will come up with. ? The obvious way is to increase the rad size and pump flow rates but he may have some other ideas.

Well, my experience of Pop and Die is when your riding in gear at low revs (probally tickover), and you open the throttle fast. Depending on where the engine is in its cycle and its load, It either responds or backfires through the carb making a popping noise and the engine cuts out. (A higher tickover cures this most of the time) In relation to overheating, if the fan was running 100% of the time, then I would be worried ! but it doesnt, so this means that the running temperature is in control. Sherco obviously had a problem early on with the prototype thats why they went to a wet ignition system.. Its not the perfect solution but it works

The Sherco's oil sump has been extended so the generator runs in oil to help with the heat generated. 800cc of oil. Theres no doubt it gets hot but it doesnt effect its performance. On a hot day the fan runs around 80% of the time. Just shows that the design is spot on as theres no wasted energy or excess weight being carried in the coolant system.

Nice looking bike that is.. Scorpa will get some serious street cred with this machine if it runs like it looks.

I got that a few times when I first got the 4T. But since i upped the tickover to around 1200 rpm it hasnt happened since.

I rode most of that day in first and second gear except sections 1 & 3 which was in third.( Section 2 I rode in second btw) . Didnt lose much grip at all and had the best ride I have ever had in muddy conditions. I know for a fact that I wouldnt have done so well on my 290. To answer your question, In the dry I use 1st when i would have used 2nd on the 290. In the wet, I normally go up a gear and any banks to go up which are wet, I would use 3rd. 4th gear is too much of a step up and Sherco may need to look at this for the 06 model. Ishy, Funny you should say that as that is what I worked out too Today, I striiped the carb down and cleaned it out and found it to be spotless. But what I did do when I put it back together, was leaving the airbox off, I tried to restart it and it wouldnt go. As soon as I blocked the air intake with my hand, it fired then went on the next kick. I aslo noticed some significant blowback through the carb also and this maybe whats causing the problem of starting it. what do you think?