oh y'know, just another build thread.

[iamhiding]

excuse the shocking phone cam quality, it doesn't handle low light very well. its amazing how much a set of tyres can change the visual tone of a bike.

[iamhiding]

so, been using the bike a bunch recently. we're coming into winter so temps have been down, starting to get snow and ice here an there and the bikes just been running without any of that punchy response and aggression i love about it and it's damn near impossible to start the last week but i've had no time to look at it.

gave the carbs a clean and a quick once over the other day and found this gem...



broken diaphragm spring. what the hell.

put me in a bit of a predicament as the carbs have a dynojet kit, ie shorter/softer springs, modified slides and aggressively tapered needles. all these elements are designed to work together to get the carbs onto the main circuit quicker from my understanding so you cant really mix dj with non dj parts and expect decent results. i've got no intent of buying dj parts either.

anyway, luckily i've got spare carbs so i went to swap needles, mains, non modified sliders and standard springs in to realise that i cant find my 150 mains, just a selection of my spares from over the years. so i just chucked the standard springs in and left the rest for that evening... damn the punch it gave the bike low down, i forgot just how punchy it is. throttle snaps shut quicker with the stiffer spring mind you but its been a while since the bike wheelied with ease. bikes running better all round understandably but its just not what it used to be. i'd put the rougher running down to being tuned on a scorching hot day and the change of exhaust.

soooo. the price of jets seems to be about double what i used to pay and i dont wanna wait for shipping so i've done something a little oldschool tonight and hopefully i'll set the carbs up tomorrow again.



note the following is inaccurate, i read it wrong. DJ is in mm and mikuni is based on flow rate. Mikuni to dj/mm mikuni150=160dj = 1.6mm. Closest drill i have is 1/16 which is 1.587mm which takes me between mikuni 147.5 and 150, which is pretty good, might be a tiny bit lean top end on my setup. From what ive read mikuni use tapered jets so the cross referencing isnt completley accurate but its close enough. Not sure if our gs jets are tapered or its just a sweeping statement
found some 115s which i'll never use again. so done a quick bit of research into mikuni sizing and i've drilled them out to 1.5mm aka 150, pic shows the difference in ID. anyone considering using the same method bare in precision is really important. afterwards i flattened back the spec stamped into the head, scribed 150 for reference with a sewing needle and dipped them in hydrochloric acid just to strip the fuel varnish off and brighten them back up. best of a crap situation but it'll get the job done.

gonna check float height and do a balance too. if its still running off it'll be compression test and valve clearance check time.

[cbrfxr67]

 

[iamhiding]

ah its always something isnt it. Annoyingly i've lost my 1/16th drill bit so ive just ordered a 1.6mm in. Now we play the waiting game

[cbrfxr67]

 
Hey you're still at it though!  Much respect!

[iamhiding]

Thanks man its just a bit of fun for the most part. The gs is a bit of a forever side project for me, itll never be finished and i'll never part with it. So many people see it as wasted time as the gs is seen as being just a boring commuter bike but Those who get it, get it though and its far from boring, its a riot to hoon about on always cracks me up, the "what... Is that?!" often followed by "fkin'ell why've you done that?!" 

The cbr fighters roadworthy at last, so that's gonna be a laugh in spring 

[cbrfxr67]

where's 'at thread and pics on the cbr again? 

[The Buddha]

Dynojet never supplied slide springs for a GS. They may have for other bikes, but not a GS.
They slowed the slide rise by suggesting you block one hole etc, so a solfter spring would be counter productive to their jet kit's flaw anyway.
Cool.
Buddha.

[iamhiding]

Dynojet never supplied slide springs for a GS. They may have for other bikes, but not a GS.
They slowed the slide rise by suggesting you block one hole etc, so a solfter spring would be counter productive to their jet kit's flaw anyway.
Cool.
Buddha.

Oh you got me thinking there, see i had a spare set of carbs that turned out to be setup using of dj parts and mikuni jets, never seemed to be quite right for 1 reason or another, it remains a mystery. Once i realised that the needles etc were dj i yoinked the bits to play with and set it up with cross referenced mikuni mains.

I had assumed they were dj springs, as they were shorter and softer like dj are on most bikes.

Anyway being curious and given that ive got a spring oddity / its a rarity youre wrong ive just had a quick look on the dynojet site. Its only giving US info on the pdfs but up to 00' they didnt get springs in the kit but 01+/F got the springs. Being in the uk im not sure if we got different kits. Ive definetley got shorter / softer springs but cant quantify their origin as they're from a set of bst33 mystery carbs however the bsr34s got them in the kit fosho'. Could be a regional thing that we got them in the uk or someone's used bsr34 dj springs... Who knows, either way ones snapped.

Yeah they plug/s the slide to slow it down, suggest removing a plug for stage 3, youre right it does seem counterintuitive, id assume the softer spring in part works with the lesser forces, to compliment the plugged diapgragm a bit more. Itll slow the diaphragm returning too, so i guess itll open quicker if its slower returning on decel to throttle modulation but also removing the plug will help reduce both the slowing effects. Its all just to bring a little more control to the aggressive needle taper so that its not on/off or lifting so quick that it gets too much fuel in that given operating range should it be opened up too quick but they also use dignificantly smaller mains. Im purely speculating and trying to rationalise their logic. Really they're just using different parameters to arrive at the same conclusion for the sake of getting it onto main circuit marginally sooner. Ive never really put any thought into why they do it tgat way to be honest. Id be interested to see back to back dyno sheets of tuned vs dj tuned just to see what differences there are and where with both stage 1 and 3. Id imagine any differences are nominal. Once again im speculating off the top of my head. Going to see what literature i can dig up on such effects purely for my own curiosity.

I love playing with carbs, i can say my experience with dj kit on the gs vs just tuning on std slides/needles is that i seemed to pick up good initial punch in the 1/8th to 1/4 throttle, little bit better as it enters mid range  but that's about it and 4/4 was good but was never quite as good as before the kit, always felt like i was between jet sizes. Cant quantify with dyno data but did a lot of back to back testing. Albeit i dunno like 5 yr ago.

I know there's certain applications ie different bikes where using factorypro has shown to be optimal rather over just jetting, think they use ti needles and different tapers broadly speaking. id assume dj has its place too but really is it worth the money to get a kit... Hell no. Thats ultimately my issue with them.

Be curious to hear your experiences with the dj kits or thoughts on any of it, personally id never waste my money on a their kits, not sure if theres any valid merrit to them but i suspect its largely gimmick.

But yeah you've got me thinking, the springs are a mystery so im gonna double check ive got the right dj needles in for the bst33s, if so it means i can run standard springs,  pull the plug/s out and tune to suit.

Once i find a cheap source of jets i'll look at comparing 1 tune vs dj tune again for a bit of fun. Sourcing the right size drills and shaft deviation have turned drilling jets into a no go for now.

[cbrfxr67]

"I love playing with carbs"