'83 XJ750E-II / RL Build

Creating a thread for my bike to track issues and previous work
Previous threads
https://xjbikes.com/forums/threads/new-bike-need-help-with-identification.128553
https://xjbikes.com/forums/threads/no-spark-cyl2-3-83-xj750.129128/

Summary until now, XJ750E-II engine inside a XJ750RL (900 frame). Bike was basically rolling but hadn't run for years before I got it.

I cleaned up the carbs without tearing them down completely, got the bike running. Idle was smooth after some fine tuning and throttle was responsive and rpm dropped back to idle quickly.

Had issues with cyl 2&3 firing, replaced TCI with aftermarket. Those issues resolved.

Replaced coil caps and spark plugs. Coils and pickups within spec

Took the HSC33 carbs to church, tore them down completely but didn't replace any parts such as o-rings or seals as no visible issues with them.

Jets seem to match xj4ever http://www.xj4ever.com/catalog/c-hitachi.html
Pilot air jet - #225: all 1981-83 XJ750E-II models, and XJ750RL models.
Main air jet - #70: XJ750RL Seca models, and XJ750E-II models.
Pilot fuel jet - #40: XJ750E-II models
Main fuel jet - 106
#102: XJ750E-II models (cylinders #2 & #3)
#105: XJ750E-II models (cylinders #1 & #4)

Wet set the fuel levels
Bench sync'd the carbs. Initially had issues with RPM jumping up straight after ignition, have since sync'd the carbs again when on the bike and it now idles stable however RPM begins to climb occasionally when left sitting at idle. If I touch the throttle the rpm increases and doesn't drop when throttle is released.

Hooked up the colortune, when sitting on idle I seem to be getting a blue flame constantly regardless of mixture screw setting (apart from when first starting the bike it shows briefly as orange).

I did remove and clean the mixture screw hole when doing the carbs.

Running stock airbox and have put a new air filter in. If I restrict airflow further from the airbox side the colortune shows orange and RPM is responsive...same as old filter. To me this would indicate there's no air leak on the intake side? Seems like I'm getting too much airflow through the carbs after the cleaning even though I haven't changed anything. Air jets are in the same position as they were beforehand also.

I've also tried spraying carb cleaner around the boots and found no leaks

Any thoughts of what to check next would be appreciated

 

Throttle shaft seals? And you are setting idle after the engine it hot ?

 

I didn't replace the throttle shaft seals at the time because they looked to be in good condition. No tears, not stretched or distored in any way. Is it standard practice to replace throttle shaft seals every time you break the rack of carbs? or only when there's visible damage?

I do recall questioning at the time whether I reinstalled them the correct way though. I'm not home at the moment so can't double check which way they were installed but can you confirm whether the 'flat/bottom' part of the U shaped seal should be facing towards or away from each carb? I'll double check they're installed correctly tonight.

When the engine is cold it needs enrichment to start up then transitions across to enrichment off without any issue

Idle was set when engine was hot

 

All rubber parts fail from age. Even if you can't see damage they can still have shrunk and be causing vacuum leaks.

The groove in the OEM seals should face away from the carb body.

 

Thanks guys. Just got home and confirmed the OEM seals are facing the correct way, continued spraying around the carbs and found a small leak on the left/outside throttle seal on carb 1. Looked around for replacement seals but have ended up purchasing some #11 orings as per another thread I found during my research.. hopefully this will resolve the issues. I'll be back!

 

Sorry if this has been asked before but searched and couldn't find.. I understand Chacal sells the o-rings for HSC33 fuel rails and mixture screws but seeing as I don't live in the US and would like to try source locally first... does anyone know the size of those o-rings?

 

I suggest calling your local Yamaha dealer as these are available from the OEM. I think you will find the part number is 9321007180