Ascot Forum

First Generation Ascots => Tech Section => Topic started by: patrino on June 28, 2018, 08:47:17 pm

Title: Jetting recommendation
Post by: patrino on June 28, 2018, 08:47:17 pm
I ended up buying a Kerker pipe for my FT.  I had a couple great offers from folks on vft.org (thanks again for the recommend, triguyracer) but decided on the Kerker.

Anyone have an idea of where I may end up, jetting-wise?  Stock engine and ignition, the Kerker pipe, stock carb, Uni foam air filter in place of the stock filter, stock airbox.  I'm going to pick up a selection of mains today and will do the work to get it right, but it's always nice to have a reference point.

Thanks, Patrick

(more-or-less a duplicate post from the Classified section ... figured it belong here since it was no longer a WTB post)
Title: Re: Jetting recommendation
Post by: patrino on July 02, 2018, 02:21:28 pm
Got the Kerker installed last night.  Fit up nicely.  Bike sounds GREAT, is probably 5# lighter, and there's a notable increase in power from off-idle through mid-throttle.  Top-end jetting isn't right (the bike splutters and won't rev out) but that's a solvable problem.  I have a couple mains, and was going to do the usual jetting dance, but just decided to buy one of the Six-Sigma kits.  I've jetted plenty of bikes but getting to and opening up the FT carb is a PITA (I was reminded of this last night!).  Not like rejetting my Yamaha DT1, where it's a five-minute operation ...

I'll keep folks posted. 
Title: Re: Jetting recommendation
Post by: triguyracer on July 02, 2018, 04:06:05 pm
Here is what I used with my White Brothers pipe with a suppertrapp end cap with 3 discs ,A Uni filter and no air box one size up on the pilot ,I made a 20 thousands shim for the needle ,make sure the needle drops al the way down if you make a shim as it has to be no larger around than the stopper on the needle so it will drop down ,I am using a 180 main jet ,bike pulls well and all the way to top end and red line in all gears with no flat spots .try it for a starting point,
Title: Re: Jetting recommendation
Post by: patrino on July 02, 2018, 04:14:17 pm
Thanks triguyracer, great info!

You're using the stock carb, right?
Title: Re: Jetting recommendation
Post by: triguyracer on July 03, 2018, 07:44:48 am
Yes
Title: Re: Jetting recommendation
Post by: patrino on July 06, 2018, 08:17:49 pm
Well, I ended up with a #145 main and a #58 pilot.

Here's the play-by-play, for the intake-through-exhaust story:

Bought the bike back in ~August 2017, got it running September or so.  Intake was filthy, so scrapped the stock filter and adapted a large Uni pod filter to work in the stock airbox.  Stock pipe, stock carb, stock jetting, stock ignition.

October 2017, read the "FT500 Essentials" and installed a #145 main and #58 pilot from ThumperStuff. 

July 2018, installed the full Kerker system.  Kept the #58 pilot, threw in a #165 main to see what happened.  Saw that someone had already installed two shims under the needle.  Off-throttle to mid-throttle there was noticeably more power.  At WFO from about 3000 it blubbered, wouldn't rev out.  I haven't jetted too many four-strokes, but it felt like it was eight-stroking.

A couple days later, got the Six Sigma jet kit.  They recommended a #145 main, with a #140 or #150 option.  They also recommended a #72 pilot jet (!), plus a couple shims under the needle.  I installed the #150 and the #72 pilot, and kept the two shims under the needle.  Started OK cold but died as soon as I choked it.  The bike was pretty "fluffy" off-throttle and mid-throttle.  At WFO it would pull up to redline (2nd, 3rd, 4th) but would still eight-stroke every now and then.  Much improved WFO operation compared to the #165, but still not good. 

Returned to the garage.  Installed the #145 main and the #58 pilot.  Less fluffy off-throttle, and revved out very cleanly (2nd, 3rd, 4th) at WFO.

I'll take it on a cruise this week or next, and peep the plug for a double-check.

Pretty happy!!!  Hope the info above helps someone.





Title: Re: Jetting recommendation
Post by: triguyracer on July 08, 2018, 04:18:39 pm
Sounds like to many or too thick of a shim under the needle there is from what I understand a lot of overlap between the main jet and the needle on a cv carb,have to admit almost all my jetting has been with round slide or flat slide carbs.Very important for the needle to be abile to drop all the way down. Make sure the outside dia of the shim is not larger than the outside dia of the top part of the needle as that is the part that bottoms out in the slide or it will hold it up and cause a rich condition in the mid range.I have no experience with the carb kit you are using but a pilot jet of that size sounds way rich unless they are using a diff way to calibrate fuel flow, lol
Title: Re: Jetting recommendation
Post by: triguyracer on July 08, 2018, 04:21:03 pm
Try the 165 with one shim under the needle and stay with the 58 pilot.are you are using the stock needle?
Title: Re: Jetting recommendation
Post by: triguyracer on July 08, 2018, 04:27:12 pm
You can drop the main a little if you are using the air box, forgot you mentioned that in your reply lol
Title: Re: Jetting recommendation
Post by: patrino on July 21, 2018, 11:09:22 pm
Update on jetting ...

I removed a shim from the needle (so am now running one shim only).  Bike running well.

Checked the plug twice, once after zipping around town, once after a ~70mph 40-mile freeway schlep (~1/2+ throttle).  Plug looked good both times, nice even milk-chocolate.