I can hear a boom boom boom BANG coming on!doh

I hope I dont hear the boom boom Bang :censored: I just like the thump thump thump ! . About the diaphragm,the 91 models sold in new Zealand dont have diaphragms so I can rule that one out . And I would rather be able to ride over two hundred miles on a tank of gas than do over a hundred miles an hour for a short while.The perfect lambda settings when it was on the dyno are 0.85 ish through out the rev range (near perfect) . So will a 86 CDI plug into a 90 model ?? I advanced the pick ups a bit by slotting the holes and it felt a bit stronger pulling out of the corners ! I,m sure the 86 models would of had a better cam profile due to smog emissions etc but I have not seen one ? Thanks guys bier

Ok, what did they use instead of diaphragm? You have pict?

An 86 ignition box will not work in a 90 . Totally different system. However, I am talking with Wieltronic and they said they could load the 86 map into a unit for a 90. You have to provide the map. They also sell a kit with their unit so you can load 2 maps of your design and provide a bar mounted switch. Steve Loomis sent me a picture of an 86 map on ADV and I am going to see if Wieltronic can load it in a box for my 90. With the mods I mentioned before you go about 100 miles before you hit reserve. I need a bigger tank.

At 6000 rpms with 47 sprocket, you will go faster than 5700rpm with 45 sprocket.

I dont ride at high revs, bet hes asking about top speed, not cruising speed or whats best for the bike.

My bike is closing in on 150.000km, I ride with everything from 13/47 to 16/45 depending on the task.

No you wont, 5980prm with 15/45 gives you 147km/h, 15/47 give you 139km/h at 5980rpm if you go down to 43 it will give you higher speed 152km/h.

I know that at the same rpm, he will go faster with a smaller rear, but that wasnt what I wrote.

I wrote that a +2 rear sprocket will add 300 rpm to get to the same speed as the stock 45. But if he cant rev out in 5th gear,the engine will struggle even more to rev with a smaller rear, reducing topspeed. This is very noticable when going uphill. So tats why he needs to go the other way, if he reall wants higher top speed. If it rev'ed close to redline, a smaller rear would be better.

I added the 1990 xt600 on gearingcommander :innocent:

His problem seems to be that he cant rev muvh past where the engine has the most torque, so to me the gearing must be too tall.

I use 16/45 for daily use, to keep my revs down when cruising, but it doesnt give me better topspeed, or better mpg as you need to rev out the gears slightly more, as they're "further apart"

Thanks for that . I think the gearing I have feels good , I dont really want to rev high all the time , but just the way it wont rev out when there is no time to change up ( when in the windy stuff )makes me think theres a problem ? Its proberly time for a freshen up . Maybe a over size piston ?. Has any one here put a big bore piston into theirs with out a hot cam and heavy valve springs etc etc and did it go much better ??

With a compression of 150psi the engine is as good as new and dont think thats the problem, question is do the engine get enough fuel/mixture and is it correct.

air fuel mixture is near perfect according to the dyno testing ,so its not that ? I shal injoy whats left of our summer and look further into it in the colder weeks :mchappy:

Cold???:palm: If you had dyno, what hp did it give you? And what about that diaphragm in the carb, how is yours built up without this?

My '80's carbs don't have diaphragms , the "90's do , maybe they use the older carbs down there? They simply rely on the piston of the slide to be close fitting to the cap bore, not the best design .

I think he is simply out of power for the too high gearing. I have several XT's and they are not powerhouses that can pull any gearing wanted. I run 15/40 in 2 and that is about all they can handle while still being able to pull fully(just barely with a small headwind @ 65mph). At most I could go down to 38 rear but headwinds would limit topend.

The advance will probably make a huge difference in the upper rpm's.

For more power a high comp piston/mild porting and big headpipe with can will get quite a bit more oomph . A better set of carbs will also greatly improve performance with some tank range loss.


TURBO !!!!

The dyno didn't have a HP gauge ? so I cant answer that one ? On the night I had mine on the dyno my mate put his SRX 600 on and it hit the rev limiter in top gear !. He didn't even know it had a rev limiter :confused1:. Where my bike in top gear as we wound up the resistance on the dyno my motor wound down and down ... we could have stalled it if we wound it on more ! It sounds similar power to JJRIDERS So maybe its normal thats good to hear , IIts hard for me to know as I have never riden another XT 600 and My 450 Sherco with 14 48 gearing will do 160 km so I expected a bit more ompf , but I would rather be on the XT for real long rides :mchappy: Horses for courses . Cheers guys bier

Hey beagle can you post pict of your carb?

Ya pics, it would be interesting to see if they put the older (or at least to the US) carbs in the e-starts down there. I don't think the carbs would cause the hp loss actually might be opposite, the boots may be smaller id than the older models, I think the US '90's bikes had a bit less hp than the '89 and older ones ,part of that because of smaller boots. I think.