The original CV carbs installed on my CB450 twin had developed a major air leak around the throttle plate shaft that I could not seal. It looks like years of use had increased the gap between the shaft and the carb body, allowing air to be sucked through. I tried several combinations of o-rings to try to minimize the leakage, and even installed extra cable return springs to deal with the extra friction, but nothing worked.
 |
O-rings installed
|
 |
Extra spring installed
|
While racing in July, the engine began heavily pinging from detonation. Investigation of the left plug found the insulator scorched and the electrode bright blue from a lean condition, so I decided to junk the original carbs before they caused any serious damage.
The VM-30 Mikuni carb kits are a bit too pricey and, I think, a bit overkill for a stock CB500T engine. Also, the stock gas tank on a 500T sits low, and can foul the carbs, so I bought a set of Mikunis taken from a flood damaged Trident. They had salt deposits internally but were otherwise fine, so I boiled the better 2 in distilled water to leach out any chunks that I missed.
The original boots are way too big for the mikunis I wanted to used, so I bought a pair of intake boots from a Honda XL175, which nearly match the CB500T's bolt pattern and intake diameter, but are designed for a carburetor with a 34mm diameter. I then machined the carb intakes to get a better fit:
 |
| Spinnin round |
 |
| Original vs Re-machined |
Unfortunately, after cleaning them I discovered that the carbs, which were advertised as VM28-49's, are actually VM26-8074's. This may be a hair too small, but they're already half finished, so I might as well try them out anyway.
No comments:
Post a Comment