RD400 wont rev video inside help!

[e30 gangsta]

Hey guys so here we have my rd400 heres a small breakdown of whats done to it.

66mm weiscos
Powerdynamo timed to 2.0 btdc, br8es plugs
30 pilots/270 mains needle clip in #3 position air jet 1.5 out.
carbs have been cleaned throughly, put in a bath, and the float heights have been checked.
yz125 reeds
k&n y boot
rz manifolds with banshee crossover tube.
dg expansion chambers.

Here is the issue I am having, the bike will not rev past 8500 rpm smoothly. Once it hits 8000rpm it start to make like a rattling noise and just runs into a wall. The plugs are perfect light brown color. The bike turns on first kick and drives great besides this issue. I cannot figure out why it will not rev past 8000 rpms smoothly. Any ideas? Someone told me that the head might be misaligned that I should have the heads doweled and possibly that might fix the issue. I have taken the head off multiple times and realigned it same issue. Another person told me its just where the pipes die off, but ive seen other rds with dgs spin past 8500rpm no problems. IM stumped please help!

In the video I do some revs then after the thumbs down, I do 2 full throttle pulls you can see how the engine clearly hits a wall at 8,500 rpms. I know I am not supposed to rev the engine without load, but I do not have a gopro to show you guys what its doing. So this will have to do. Any help would be greatly appreciated. Thanks!

https://www.youtube.com/watch?v=K2h-EgiDk7Y

 

[teazer]

Spark plug color tells you very little unless it was as a result of a full power plug chop. Revving the bike like that doesn't tell us much because it's not under load.

270 mains a re a little large for teh mods you made - under most circumstances, so it would be good to run it on a dyno with Exhaust Gas Analysis to see what the air:fuel ratio is doing across the rev range. You could get a UEGO kit but a dyno run or 3 are cheaper and safer.

Does that PD system include a curve or is it fixed timing? It would be good to know what the timing is at 8,500 and see if it's too advanced or retarded. Too far either way will hurt revs.

The engine sounds a little loud which could be piston slap or mild detonation. What is the piston to bore clearance? And what is compression like now? Are the crank seals new?

If timing and air:fuel turn out to be fine, try the stock reeds and see if that makes a difference. On a stock motor it is possible that the stiffer YZ125 reeds are too stiff and not opening far enough. How far do the reeds open - stock 8mm or did you modify the backing plate to allow more lift and iif so by how much?

 

[e30 gangsta]

Ive done plug chops all is well in that department. No access to a dyno around me. The powerdynamo is a fixed timing unit set at 2.0 btdc. Compression is 180 in each cylinder with new crank seals, the yz125 reeds were just installed with the third reed cut off and installed into the stock cages. Engine is loud due to the weiscos I suppose. Thats all I can answer because this is all the information I currently know. Going up on the mains makes the bike very sluggish and rides horribly, and going down gives me a white/lean plug. I am stumped.

 

[teazer]

Plugs are supposed to be white at full noise. The only place you expect to see color on a flat out chop is down inside. Check the electrodes for signs of overheating and it the color is OK on the electrodes, it's not as lean at full noise as you suspect.

On the street, clean on the mains at the top end and richer on the needles seems to work well because most of street miles are done on 1/2 throttle on the needle and needle jet.

See if you can find a pair of #284 needle jets from a Euro spec 400E/F or a pair of LEDAR N/Js with taller spray tube.

YZ125 3 petal reeds are popular but on a basically stock motor it is possible that they are too stiff. I used to like the old two stage Boysens on a street 400.