Do i need a rejet, or is this something different ..

Recently fitted a new engine, tis running quite nicely, bar a little whizz/ rattle fromthe front end, it's prob the cam chain tentioner...but thats something to do another day.

I've noticed two main things that concern me.

1) In 2nd gear around 4K - 5.5K Rpm we've got no power, or the power we have in terribly lumpy, to the point where the bike is actually rocking forwards and backwards.

2) When we finally get up a bit of speed, say to the 100Mph mark, and above it's rather difficult to maintain a steady constant speed, now im aware of the engine braking on the SV's but surly it shouldnt be that strong around the 100mph mark, the best description i can give is that it feel like i have to constantly apply more throttle to maintain a constant speed.


I've a K n N filter in there, with standard jets, and a CCC Can the carbs were balanced recently. but again she's never been rejetted.

A rejet should help, is the engine standard internally?

Originally Posted by Dangerous Dave

A rejet should help, is the engine standard internally?

Yes Dave it's standard internally ...altho i would like to put a set of cams in her, that can wait ..

I can understand the jetting sorting out the flat spot in 2nd, but does it explain the constant deceleration ?

Originally Posted by drag

Yes Dave it's standard internally ...altho i would like to put a set of cams in her, that can wait ..

I can understand the jetting sorting out the flat spot in 2nd, but does it explain the constant deceleration ?

Obvious thing that causes drag is brakes. Get up to speed and pull the clutch in and see if the deceleration is the same.

Originally Posted by petevtwin650

Obvious thing that causes drag is brakes. Get up to speed and pull the clutch in and see if the deceleration is the same.

Good suggestion pete !! never though of that one.

I'd kinda ruled out the brakes as she seem pretty good down the low end, 40 - 70 mph ..but there again it's hard to say

[northwind]

I'd be suspecting fitment tbh... What you're describing sounds pretty lean-ey but your mods shouldn't cause it to be that bad, so I'm thinking maybe you have an air leak somewhere. Just using the usual "check the obvious" and thinking of things that were changed in the engine swap first.

An air leak .... some where around the carbs .... now i assume a dyno run would be able to highlight this if that was the case ?

And even tho im running a standard enough kit, i'll be adding tank spacers soon enough, and mayb change over to a bmc filter, it's prob worth my while gettn it rejetted.

[yorkie_chris]

no point dyno'ing it, just visially check the carb clamps are tight etc etc.

If you fit any other filter you need to rejet after.

i had the same prob, when i fitted some rejetted carbs. i did not lift the tank at first.
the same feeling at 100 mph that something was holding it back.
lift the tank and the bike was set free, the engine rev'ed free. no more holding back at 100, just keeps going,

Originally Posted by stevegb

i had the same prob, when i fitted some rejetted carbs. i did not lift the tank at first.
the same feeling at 100 mph that something was holding it back.
lift the tank and the bike was set free, the engine rev'ed free. no more holding back at 100, just keeps going,

Perhaps when they re fitted the carbs + engine they blocked the air flow some how ... i'll investigate this weekend so