Engine Cuts One Pot When Reved

[ddelectrical]

Hi. The HT leads were new with the coils. Both coils showing about 15k Ohms on secondary windings. Heat shrink on the cold start plunger shafts doesn't work. It goes tacky with petrochemicals. Jams up plungers. Removed sleeve and had a real close look at the plungers. Not the best design by a long way. Little plastic needle and flappy stainless thing. Very interesting to note that by 1999 the TDM was fitted with BDSR 38mm carbs which have metal cold start plungers and all internal fuel gallery! Like they always used to be. Unlike the BDST carbs fitted to this 1997 model with its plastic plungers and external brass fuel pipe. Also noted that the XTZ750 always had the BDST carbs and never updated. Wonder if owners of these had similar problems?

 

There is residue around the area where the plungers clip into the body. Something is leaking for sure. There's a few carbs of similar age on ebay showing similar residue.

 

I'm going to seal the carbs and blow some smoke through them to see if anything leaks. Hard to tell by vacuum cleaner test so pressure test instead.

 

Next up is plugs out again. Check colour. Watch sparks. Down pipes gave same temperature readings from cold start with infrared thermometer on last run up. Oh for a thermal camera though!

 

I haven't separated the carbs from each other yet but I am wondering if one of the link pipes has an air leak too.

 

I tried the hand over the carb trick but before finding and replacing the duff spark plug. Hand over left carb - engine dies. Hand over right carb - engine just about continues to run but laboring. Hence why I think it is sucking air into the right carb somehow. Manifold rubbers / o rings all fine. But then again it could have just been down to the faulty plug. Didn't check it again before taking carbs off this time. Opps.

 

Good tip about pulling spades from coils. Safer than pulling plug caps. Thanks.

 

To the bat cave..............