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dynojet kits


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Posted (edited)

Am i right in the thinking that turbos dont like carbs with dynojet kits previously fitted? I have a set of stock carbs at the minute (bandit 12) and i want to run it as is no turbo to make sure everything is working fine before carrying with the turbo idea. its and b12 motor in a 750j frame with a few other mods. now i need it to run fairly well in the meantime, so if i fit a dynojet kit am i i gonna fuck these carbs up for turbo use. cheers guys

Edited by wobblegob
Posted

Should be fine as you'll be changing back to stock needles for turbo use. Any jet changes are easy to swap back of course. So long as the slide lift holes do not require enlarging everything can be swapped out as required. Have you the standard Airbox fitted? If so, i'd just stuck with stock set-up until you are ready to turbo. Saves dyno time/money that could be better spent on go faster bits. 

Posted

Interesting point ! I can't say I've seen any post or question here regarding use of DJ fitted carbs with a turbo. In practice, the DJ kit is fitted due to the loss of airbox & other airflow related modifications and they work well in this respect. I can't see any reason why they would not work as well when having forced air blown through them! Whilst standard settings / jetting can work - is it optimal ie. std. needles are shaped to deliver a leaner cruise mid range - just when a turbo is starting to make boost so not ideal. As most dyno tuning is only done at WOT, i'd guess no one knows exactly what is happening in the mid-range most of the time. Who's going to give it a go? :/

Posted

Indeed DJ kits are not helping. Part of the kit is drilling larger holes in the slides and softer springs so they go open earlier/faster. I had  problems with that in my previous carbed turbo setup: always got rich stumbles the moment boost came on.  Replaced the needles, slides and springs with stock ones and behaviour was good.

If the carbs are modified well, jetting and needles are close to stock. That also makes the AFR not sensitive to variation in boost level.  I had 340rwhp with stock 125mains running nicely at WOT with 11.5:1 AFR and still have good off-boost behavior and decent fuel consumption when driving normally. Key was having pitot tubes facing the middle of the airstream  going towards the bowls. (I had 40mm original  carbs, 2 pitottubes each going to the stock bowl T connection, pitottube 8mm which is 6mm bore size and 2" uppipe that contains the pitot tubes. Dont connect anything else to those pitot tubes as it messes with the function. No additional T's, nothing. Its sensitive)

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