Model 97 Mods - Carburation

[Zyx]

Has anyone ever tried running a 28 Mikuni on a 97 top end? I was wondering if it might mitigate bogging tendencies at lower revs. I have an entire assembly from GEM reed block out for the 28 Mikuni and was thinking of trying it just to see.

As it is, the engine runs great, but being a dedicated MX engine but with a wide ratio transmission installed, it tends to bog a bit if I let the revs drop. No surprise here. But I ran a Webco 125 kit on a 93 bottom end for two seasons of cross country racing with a 24 Mikuni, and though never a fast bike, it did better than well. Started 400th out of 450 in Kentucky in 1974 in a hare and hound, and finished 8th in a two hour race, so I know smaller carbs can work.

I was thinking that if this works, the 28 would be better suited to things like the Bad Rock ride, while the 32 would be best for scrambles tracks or moto.

Anyone have first hand on this with the 97? Porting is stock, but stock exhaust is a bit drastic as built. I know I can't really change that, but thinking I might get by with the carb swap.

[hodakamax]

AZ, I did put a 28mm/GEM reed combo on my 94A for the ISDTRR in Oklahoma last year. It just has the iron 94 cylinder and mild porting but I was really happy with the low end and even brisk top end. It also has a Combat head and Circle F pipe. Anyway, It's a good combo for serious trail. A stock 97 probably has a higher exhaust port than mine and it's killing the bottom end a bit. All speculation here, the last bikes ordered out of my shop were Combat Wombats. Never messed with a 97 but I have ridden them and they did seem a bit peaky as I remember. Everybody's probably tired of seeing it but I never pass up a chance to post it one more time.

Later--

Maxie

PS--the post "Combat Wombat Air Boot" discussed what to do about the Air Boot after you have put a reed valve on. Check in the picture (blow it up.) and you can see how far the bottom of the air cleaner has been moved back.

[BrianZ]

Just as a "FYI", the model 94/95 has different cylinder manifold spacing than the model 97. So if you have a model 94/95 reed valve assembly it will not fit the 97. I found out the hard way, when I bought a 97 reed valve assembly and tried to fit it to a model 95.

Brian

[Zyx]

For what is worth, I am going to try a model 98 flange and airboot on the model 97 reed assembly to see how that fits up. Near as I can tell the two reed blocks are the same. My earlier GEM has different four bolt spacing but not that far off. I thought about slotting mount holes, but if he 97 and 98 reed assemblies are the same or same bolt spacing anyway, seems like the 28 I have should slip right in. I will let the group know. Most folks don't start with a 97 when building a trail bike I guess probably because of the pipey porting. But, having ridden a torquer for years, I kind of like the punch this 97 has. It just needs a little help to get over the gasping at low end. All I can say so far is had I had this much power when I was 24 I would have been a lot faster. It just isn't as forgiving as it could be. But it is better than some others I have tried, like old Suzukis and Hondas that had no go whatever under 5,000 and couldn't seriously be ridden on trails without punishing bike and rider.

We will see once parts arrive and I get home to put them on. Running livestock this weekend in Nevada with my Aussie. If you think old bikes are expensive, trial and train a champion dog for a year.