Second Generation Ascots > Tech Section
removing the stock airbox '83 (shadow)
J6G1Z:
I just ordered a Dynojet carb kit to see how that works out. I've always wanted to try one of these kits. I just don't know if it will be rich enough for the filter & exhaust modifications.
Thanks for that link. I didn't know about that group. I'll have to check it out some more.
Here is one post that I think is worthy of saving.
The plenum is the key- multiple CV carbs like to breathe 'common', 'calm' air, so a K&N on the tail end (or inside the OE box) could work well. Briefly; I have K&N type mesh filters, each mounted on a 6" long swept-back 50mmsilicone hose. Mains are #130 front, #135 rear. Needles shimmed up 2mm & slides drilled to 3.2mm, pilots are both #40.....
Thanks
J.
J6G1Z:
Just in case anyone else is interested...
You need a filter with a 3" I.D. to fit the intake plenum where it attaches to the airbox.
I picked up a UNI model #UP-6300AST. It's a 2 stage pod with a 3" I.D. inlet & 6" long. It also has a 15 degree angle on it.
It fits the plenum opening perfectly. I have not removed that air-box to see how well it fits into that area yet, but I don't expect any problems with fit. I may need to fabricate some brackets/braces to hold the coolant recovery tank in place. That remains to be determined.
Thanks
J.
J6G1Z:
Well I tried this experiment & the results were not great.
I removed the complete air-box assembly along with the oil seperator & the coolant recovery tank. I found that my coolant recovery tank was dry rotted enough to have a hole right above the current coolant level. Any higher & it leaks. Not good! For now I'm using a tall prescription bottle as a temporary coolant recovery tank. It's working.
Once I removed all those parts & cleaned up the area in the center of the bike, I removed & inspected the air intake plenum. I found several areas where the sealant around the carb boots had rotted away & was potentially letting dirt inside. I cleaned up the plenum inside & out, then I re-sealed the carb boots with some black RTV. I ordered a large UNI filter & installed it onto the end of the plenum. There is plenty of room now & the side panels fit like normal. It is a great looking modification, but unfortunately the bike doesn't care for it one bit. I believe that it is just too much air for the carbs to handle. I installed the DynoJet kit with the richest jets & it still wasn't enough. I think that someone who is real sharp on jetting CV type carbs might be able to make it work, but I don't have that type of experience.
I re-installed my air-box after modifying it some http://ascot500.com/index.php?topic=291.0 and now the bike runs much better. I still have a bad spot after 5.5K RPM, but I just received the next two steps richer jets to dial it in with.
If anyone has anything to add to this post, please do.
J.
cdntfindanAscot:
I did try some basic messing about without any success so I am back to stock at the moment. :(
For anyone experimenting, this is what I tried. (save you the time trying it out ??? )
experiment 1.
I removed the whole airbox and clamped the OE filter to the plenum - thinking it would be the same volume/ rate of air flow as stock. and the result was a resounding 'No!' - I could not open the throttle more than fraction before it bogged down. I deduced from this that the filter does not slow or reduce airflow in any way. So it must be down to the air 'intake' hose size .
experiment 2.
removed the intake bit (snorkel?) of the stock airbox and connected that to the plenum, (no filter). The result this time? slightly better than air filter only but still completely unrideable again bogging down as soon as the throttle is opened.
My final deduction being that the volume of stored air in the stock box also plays a big part in the engine running correctly :o
My next sometime in the future experiment will be measuring the internal volume of the stock airbox and making another different shaped one (shallow, oblong to run directly under seat pan, with oe intake snorkel on one end and the plenum on the other) and see if that works. If it does then there is plenty of filter material available loose to then fit in said box.
It will probably be a while before I get round to this though, I am making the most of the nice riding weather :)
scottly:
--- Quote from: J6G1Z on July 11, 2014, 04:32:46 pm ---
I re-installed my air-box after modifying it some http://ascot500.com/index.php?topic=291.0 and now the bike runs much better. I still have a bad spot after 5.5K RPM, but I just received the next two steps richer jets to dial it in with.
If anyone has anything to add to this post, please do.
J.
--- End quote ---
Sounds like the snorkel is indeed a major restriction. ;)What size main jets were stock, what size jets have you tried, and what size jets did you just receive? My experience with the FT CV carb is that it's 90% a main jet issue when you allow the motor to breathe.
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