First Generation Ascots > The Thumper Years: Stock To Lightly Modified
Carburetor rejetting question
frappy:
Just purchased a new-to-me ’82 FT500 with 3,300 miles on it. Entire bike including engine and exhaust are bone stock. It seems a little hard to start and feels a bit underpowered when riding down the road. However it runs smooth if I ride away with the choke on when cold, and will idle fine once the engine’s warmed up. I am keeping this bike on a trickle charger and the battery is showing xx.x volts across the battery terminal at idle.
Maybe it’s just me being picky, or not knowing the exact starting sequence. However, it did not start the first time for the PO as well, and I am wondering if that is a symptom of simply the carb needing to be rejetted, or if there are other issues. The bike eventually comes to life, but maybe after 3-4 revolutions of the starter when the engine is cold or has been sitting awhile.
I would like my engine to come to life on the first or second revolution of the Ascot’s fragile starter motor, but it doesn’t. Maybe I just need to learn the starting routine, but after reading the “Ascot essentials” article, I went ahead and ordered the 2x oversize jets from Mark at Thumper Stuff, in hopes of getting my bike to fire and hold idle a bit more quickly. I could just go ahead and install the jets, but am kinda’ curious before I do as to what are the specific advantages of the upgrade.
For instance, once I install the new jets and a new float bowl gasket, will my FT500 start more easily when cold? Will it need less choke? How well will it start when warm? Will it have better performance off idle, at certain RPMs, or everywhere in the power-band? Lastly, are there any other adjustments I need to make to the carb once I install the up-sized jets?
In the long run, I am hoping that the new and bigger jets will help my bike to start a little easier, perform better, and relieve some of the stress on my starter motor. Thanks again folks for your feedback.
FT500R:
What really helps for me is to open up the throttle twice before starting the bike. It usually fires right up even without the choke.
This is with the standard jetting.
J6G1Z:
The new jets will help cold starting somewhat, but mostly they resolve the lean burn condition that exists in OEM configuration. The new jets will provide a bit more power & allow you to add one or two teeth to the countershaft sprocket. I chose to upgrade to a 16 tooth countershaft. Stock is a 15 tooth. The larger countershaft sprocket allows the engine to operate at a lower RPM range.
There is a starting procedure that you can use to help the starter. Remember that the carb has an accelerator pump. This is a very nice feature. The accelerator pump squirts a fine stream of raw fuel into the carbs intake tract when you rotate the throttle. This is to prevent the engines tendency to hesitate when the throttle is whacked open. Use this feature to your advantage when starting. I usually rotate the throttle about 3-4 times to prime the carb. Plus I use the full choke when the engine is cold. Make sure you push the start button right in the center & hold it down firmly while starting. Of course you need to let off as soon as it fires. I have a few Ascots & they are all cold blooded. I usually let the engine warm until the cylinder is warm/hot to the touch. Even then I usually need 1/2 choke till I ride to the end of the block. Use that choke as much as required & don't be concerned with it. Before starting, remember to prime the carb by pumping the throttle 3-4 times & see if that doesn't help.
Good luck
J.
frappy:
So, I've pulled my FT500 float bowl and jets. The existing stock jets I removed from my carb are Pilot Jet 52 and Main Jet 140. They are both marked as Keihin jets. The jets I got from Thumper Stuff are Pilot Jet 58 and Main Jet 145. Are these new oversize jets going to create a problem? My FT500 is bone stock California bike. I thought we were supposed to go two (2) sizes bigger? Will the +6 Pilot Jet and +5 Main Jet work, or do I need to get smaller "oversize" jets? Any info/guidance from more experienced Forum members would be most appreciated. Thanks!~
J6G1Z:
You have the correct jets. Keihin jets are numbered oddly.
Did you have any trouble removing the low speed jet? I almost stripped the slot out of mine.
J.
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