ok Gents, apologies for the delay in comms. has proven most challenging having an aircraft parked 400kms from where i live. since the original posting I'm now licensed and have my L1 certification, so it has bee quite a busy month. Continuing on with the throttle hesitation issues between 3500-4000rpm i suspect that poor workman ship is to be the most likely culprit. Couple of things i wish to share, given the community has a wealth of knowledge and i fee obliged to return the favor for other aviators with similar issues.
- Carb vent lines were inspected and found one line had been cable tied against the engine support frame. (line was squashed) also wouldn't haven been helping the issue.
- one throttle control linkage (on the carb) was bent. was removed and straightened, both idle stop positions rigged so they were identical.
- one carby choke linkage was sticking, may not have been helping but was freed up with no issues.
- the diaphragms were removed and inspected. upon inspection there was physical debris under the diaphragm seats on both carbs. The rubbers were quite soft indicating they had been changed recently (no log book entries to say otherwise, purely a speculation). The pistons were cleaned, as were the seats and both carbs reassembled. This has actually appeared to have rectified the issue. the response is crisp and doesn't hesitate.
In a nutshell i think a lot of small things have lead to a big issue. the dirt under the seats could have been possibly been the most likely cause. I was hoping to take some photos and make this a little more visual, but when your focused on the issue at hand, its easy to forget to take the occasional happy snap.
again as a first time forum-er id like to thank the community for their assistance.