www.gpz-305.de

Simon Smith · Anmeldungsdatum: 17.05.2006 Beiträge: 1 Status: **Offline**

Hi,

Really great to find a site for the '305.

I have a 1985 GPZ305, which has had a very chequered history. Suffice to say that it is now the frame, forks, wheels and carbs from the original bike, an engine from a 1988 bike which was written off when it caught fire (my original engine threw a main bearing) and bodywork and electrics from a 250 Scorpion (my bike was nicked, trashed, recovered and eventually re-built).

Ever since I first had the bike, it has never pulled smoothly at med-high revs. Before the electrics were replaced, it simply wouldn't rev over 9,000 rpm. Now it is running again it will get to redline but is prone to misfiring from about 7,500 rpm and final power is certainly lacking. The carbs have been stripped, cleaned and checked twice but I had a real job to get the float level so they wouldn't flood. Pilot screws are set and carbs are balanced, low rpm running is perfect, although the bike gets very viby 5,500 to 6,500 rpm. Very smooth around 7,000 rpm (good motorway cruising speed) but rougher over this.
As for the electrics, have tried different plugs, coils, HT leads, swapped CDI's, and although these had some impact on running the misfire persists.
Personally I think it's the carbs, but what? Any help or advice would be greatly appreciated.

Lothi · Verfasst am: Fr Mai 19, 2006 11:15 pm Titel:

Hi Simon

First check if You have the power-reducing carb-valves for 27HP.
Strong power between 6000-7500, lack of power below 7500 revs is typical for the 27HP-version.
look here: http://www.gpz-305.de/Tipps/GPZ-305_Vergaser/valves_b.jpg

some backfire can be from a closed drill between the exhaust manifold and the mufflers. The drill has to be there for getting additional air to avoid backfire.

For final power it is essential to adjust the carbs with a vaccum gauge. otherwise it is not possible.
Read this : http://www.gpz-305.de/English/Tips/Carbs.html

Vibrations are not usual !
If there are quite a lot of vibes:
- Carbs are not in sync quite well
- engine mounting bolts or rubbers are not tight
- framework has small cracks
- clutch is not mounted properly (acts as a countershaft)
- a bearing was rusty and is broken now (lack of power, some vibes) -> check drained oil for metal-flakes or small mtetal balls

Maybe there could be some problems with:
- sidestand-switch (ignition disrupts periodically due to special vibrations)
- mufflers hampered by rust-partcles
- air-cleaner or airbox (intake) is blocked
- valve-clearance
- pick up coil for CDI is defective
- tensioner-spring of the rocker-chain is weak
_________________
Grüsse

Lothi tach