Bad throttle response?

[Jpich85]

I'm happy with my rf900 engine swap but I have really bad throttle response, I especially noticed if riding my 1990 750 and seeing how smooth it is, I just wondered what might cause this or how I could try and improve it, I have pod filters with the 900 bottom end and the 750 head, I've got 147 main jets. Cheers

[Madb]

hey, how do ya mean by bad thottle response?  does it feel like your twist grip is connected by a rubber band, like you  open the thottle and they're is a delay before something happens or just doesn't get up and boogie?

[Jpich85]

Hi madb, yeah it doesn't have a nice smooth build up through the low revs but only once you've closed the throttle and then open it back up, like when you're slowing at a junction or round about, it sort of like jumps in rather than a nice smooth build up, it doesn't bog at a all tho.

Cheers

 

[banoffee]

Dyno run? Read the dynojet troubleshooting guide?

[Jaydee]

Check all 4 diaphragms for any tears especially at the edges where there weren't seated properly. Usually feels like a delayed throttle response because poor air vaccuum to lift and drop the slides due to leak. Easy one to check.

[Jpich85]

Cheers boys I'll check that out, it runs fine it's just not smooth on the Rev build up when at low revs

[Madb]

Thing is Jpich85, when one removes the air box especialy on cv carbs the reponse does tend to suffer , but as the guys have said check the above, as i am running the 750 ecu and timing wheel i am running with more advance so does tend to boogie . do you have the 750 ecu? if you do have and use it just don;t rev it anymore than 12000. i have'nt got near that ...yet. not rev it more than ten thou as yet ! hoping weather stays nice so i can go out tonight and boogie shum more! fuel figures seem very good at mo but its running high gearing. wot gearing you using at mo? mine is 15 front 42 rear. rear spocket with be 45 when it arrives. then ....... Super whooooosh will be happening!

[Jpich85]

I have the 750 ecu too madb but I don't think I've put the 750 timing wheel on? Is that something I should do? No I haven't revved it that high, I'm like you think I've got it to 9k and thar was fast enough for me lol, I'm running 15 and 45 gearing I thought it would wheelie more but as my throttle response isn't good on the blip. With my new build I'm thinking about keeping the standard air box but it looks so ugly on a custom bike I think.

Cheers boys

 

[Madb]

this convertion ( RF900+750w head) seems a lot softer, more like a rugby player  than a sprinter if you see what i mean. but that Torque button  makes up for it! you could make it more zippy by fitting a six speed box but it involves some engineering, something i've been investing in. I'll post up shum time soon about it.

mine came with a 750 timing wheel so previous owner maybe had same thoughts. it will be marked "17E" if it's 750.

[Jpich85]

Thanks madb I'll check see what mine is, I know I guess when you mess with an engine like this, it won't be like a factory tuned bike unless you had it professionally done, just have to enjoy the ride and make sure it's safe :-)